I believe artist think their art is bad sometimes because they are look and think about the most so they can spot flaws and misexecutions in their work. I can admit I have these moments too, but I have to remember if I am not good how come I can draw the human adult with almost perfect anatomy?
Personally I usually think my stuff looks terrible and for a lot of reasons actually. Partially because I'm still trying to get my digital stuff to look half as 'okay' as my traditional stuff, partially because I generally want to be better since I feel like things don't turn out the same way on the page as it does in my head...
But in general, I think everybody wants to be better at the craft no matter how good they are, whether they're just starting out, or whether they have amazing stuff, and maybe the better people get, the more they notice what could be better and the higher the expectations of their own skills become. It's not really a bad thing, since in a sense it pushes an artist to get better, but it is a crummy feeling to slave away at a piece of art, finish it and then while everyone else is saying how good it looks, you think 'it could be better' or 'the eye is not quite right'. It's a little frustrating at times, but it's a great driving force to keep at art and see more improvement I think.
I'm one of those weird artists who is usually pretty proud of my work, hahaha. When I first finish it, I'll be really happy with it and want to show it off... and then a few months down the line I'll kind of be like "ugh, gross"... but even then I can recognize that it's still good work?
I think the self criticism comes from the fact that you spend SO LONG looking at your own work that you can see everything that's not perfect about it. But someone else is only going to look at it for a minute or two, not the hours you spent staring at it, so chances are they won't notice all the flaws the artist does.
From personal experience, hate like that is largely rooted in disappointment. You spend your life watching and admiring other artists and begin setting standards for yourself without even realising it. Then, equipped with what's possible, you begin imagining pieces you might create for yourself, only it isn't your style you're imagining, it's someone else's. You spend hours trying to put those thrilling scenes onto paper, and time and time again it doesn't look right. Nothing goes to plan. Soon every piece you make is a reminder that you just aren't there yet, and you begin to hide your work from other people in case they misjudge your mediocrity for complacency. Or worse, they mistake your lack of shame for pride. You start to draw only in secret, and when a piece is accidentally discovered you brush off compliments because you simply don't agree. Or your afraid their only humouring you. You insult your work and kick it around because you don't feel is deserves any praise. It's the deformed child of your dreams and reality, and you'd rather lock it away in the basement where no one will ever find it. It's not hate, though. It's disappointment yourself, at least in my experience.
I'm fairly new to comics and on a steep learning curve so the vast majority of my stuff I can see problems with. I don't hate it though, and it's good to see the improvements over the months.
I think the important thing for me is that my latest comic has less problems than earlier ones. And if I keep that up I'll get closer and closer to producing something I'm really happy with.
I've had this problem before, but I learned that instead of just hating on your own work, but see where and how you can improve it.
Guys, don't blame your hand unless you have a condition that makes it difficult/impossible to move your hand in a precise fashion. The problem is your brain.
The 'crystal clear' imagery in your head is not actually crystal clear. The clarity is only perceived, felt, but is not real. If you could really see it in your mind as clearly as you can see an actual picture, you should be able to trace your own imagination on a blank sheet of paper. BUT YOU CAN'T!
Anyone can get a "clear" vision of, say, a cute rabbit rolling in the grass. But just because you can "see" it in your mind, doesn't mean you actually know what a rabbit even looks like. I don't, even though I physically see those fluffballs in my yard every night in warmer months. Long ears and fluffy tail, sure, but head structure? Body proportions? Nope! The clarity is not real.
Hmm. From my experience, it seems like the only "artists" (using this term generically to mean any creative field including but not limited to film, modelling, etc) who ever seem fully content with their work are the ones that wind up delusional about the quality of it.
Artists who are passionate about their craft have a specific goal in mind. They can't be happy until they achieve it. It looks like hatred outwardly, but it's really not. In a way, it can be it's own form of happiness. As you continue to rip apart and analyze your work it paves the way to new heights. I think it's quite healthy to be disastified with your work. Some should just remember more often to look back on what they have achieved in the process.
I think it's because many of us look for perfection, and mostly our mind can recreate the perfection we want, but when we draw it, well, sometimes it doesn't go as we want.
I used to dislike my work (dislike, not hate), but later I thought something better, instead of look at it like "ughh I failed with this #&@$!!" I started looking like "ok, it's not good, but it's not that bad, could have been worse" and then I see which parts in my work I improved or that looks good
We have been staring at our own work since we started drawing. By the time you finish an illustration you've been eyeing it for hours on end, picking out all the things wrong with it and all the details you would change if only you had a steadier hand and more patience, alas! But when you look at someone else's work you don't just see the details, because you haven't been staring at the piece so long that it's become disjointed; you see the whole picture, instead of the spot where the artist's hand twitched and the linework got a little loose, or the places where it doesn't match their vision for it. An artist tends to see their own work as boring and riddled with little problems, so when we compare it to artwork we haven't been heavily critiquing for years it looks "bad."
I think its a combination of the kind of people art attracts and the sort of person art turns you into. Scrutinizing every detail knowing where you took shortcuts, thinking what if I spent 8 hours on it instead of just 2? A lot of artists evolve to be their own worse critics because becoming content can mean the same as stop improving, I dont think there is any artist so content with their style that they don't at least make minor tweaks or incorporate something new every once in a while.
There is also the whole trying to get out what is in your head out into the real world and that is a whole other bitch and a half.
I think we're kind of nervous when we show our drawing to others I mean you draw the best you can and take time on it we don't want to hear something negative about it so we say that is bad and terrible so the person will say nah man that's really good drawing ( maybe that's me lol )
or we have goal to reach I mean if you don't see the flaws on your drawing you can't get better .so I think that's a good thing 
This is exactly what it feels like to me, as well. You really hit the nail on the head, dude. I just look at the artwork that I do, and I think to myself, "not bad, but it looks so much better in my head...".
lol.
I gotta say, I dont see my comic art as throw away, I actually think thats an unhealthy view of comics in general and something that a fair few people in the industry are trying to combat. If we cant take ourselves seriously, why should anyone else?
There are some pretty outstanding and beautiful comics out there, award winning in fact. This I think is the standard we should be striving for. And yes, there are some mass produced and sometimes less than perfect comic art, this fills a market, but they arent the ONLY type of comics on the market. Thats like saying reality TV is the ONLY thing on TV. There are groundbreaking drama's, smart sketchshows etc etc.
So don't get into the mindset of setting the bar so low to start with, aim high!
anyway, I've gone WAAAAAAAAAAAAY off topic. sorry folks
I think its because, when you look back, there's a LOT of stuff that you wouldn't do today. It's also the feeling of "wow ive come this far and i made this before, yuck". I guess since youve improved so much you just rise over your previous drawings, youve naturally evolved and rather not look back. Man, thats heavy.
I don't hate my work.
Even though I'm a perfectionist, I push that off to the side when I draw.
Because doubt consumes an artist whole.
I don't blame my hands for getting something wrong, nor do I blame the tool.
Instead, I look back at what I did, and see how much I've improved since then.
Okay, I think I may have not conveyed my point here in a clear enough manner.
It's not a comment on the quality of comics themselves but how comics are read. You can, and do, have comics which are showcases of great artistic skill, BUT the general public (not all, but many) do not look at your work, not matter how good it is, for more than a few seconds. They come in, read your page and then go elsewhere.
Hell, even the 'fine arts' has the same issue. You take a year to make painting only to have people look at it for a few seconds in a museum. And those people had to make the effort to actually go to the museum in the first place!
You're a critic of your own work because YOU know what it's supposed to look like and you've been looking at your work for hours or even days.
ahha, so this is the point your making 
http://sugarfiendgfx.tumblr.com/post/127232939752/leseanthomas-leseanthomas-omfg-this28
I've struggled with this for years (Like...13 years) and have only recently gotten to the point where I won't reflexively criticize my work. Everyone who posted has made some really good points and I agree with.
What I do want is to share is this quote by Ira Glass that I think every artist ever needs to hear (heck it works for anyone in any field tbh, especially creative fields). It's this: (Just the first half)
Nobody tells this to people who are beginners, I wish someone told me. All of us who do creative work, we get into it because we have good taste. But there is this gap. For the first couple years you make stuff, it’s just not that good. It’s trying to be good, it has potential, but it’s not. But your taste, the thing that got you into the game, is still killer. And your taste is why your work disappoints you. A lot of people never get past this phase, they quit. Most people I know who do interesting, creative work went through years of this. We know our work doesn’t have this special thing that we want it to have. We all go through this. And if you are just starting out or you are still in this phase, you gotta know its normal and the most important thing you can do is do a lot of work.
There's still a bit more to the quote but this is the key of it. I think artists, at a gut-level, notice that their art is lacking that 'special something', I like to call it. And it's different for each artist.
But what I'd like to focus on is this: We get into comics and art because we LOVE comics and art, right?
The problem enters when we start comparing to others and then berating ourselves. I'm not saying it's easy to pat yourself on the back when you feel like you don't deserve it, but here's the thing: You do.
You do deserve it. You deserve the fact that you're here and your making something. More importantly that you're finishing something and uploading it! The majority of people DON'T create because they're paralyzed by the fear that it'll never be as good as they imagine. Not letting that stop you no matter how much you criticize yourself, I believe, is a sign of strength.
I want to mention that it's equally bad to be full of yourself or your art. A healthy pride is one thing, a bloated ego is another. But sometimes I believe that artists ought to, at least privately, indulge in their hard work; compliment themselves and tell themselves that , "yeah, I did good work and I like my work." Even if it feels selfish, especially if it feels selfish. 'Cause it'll only feel like that at first.
I don't believe learning to like your work will make you want to be lazy and sit on your laurels; if anything, from my experience, it makes me work harder to make even better work.
When you feel good, you produce better work. I draw every single day, mostly because that 's what professionals do and I want to be a professional. I notice when I"m bright-eyed and bushy tailed in the early mornings, my work is really good, and I enjoy it, even with the flaws and mistakes, because my mental atmosphere is positive. The same is true in the inverse.
Gosh, I wrote a lot and I have strong feelings at this topic xD If you coudln't tell.
But for the TL:DRs who scrolled down I just want to say: Allow yourself the criticism, but also sneak in some praise. Start tricking your brain into some treats if you can't get yourself to stop at your criticism. Or at the very least, begin to catch yourself or at least NOTICE when you've begun to criticize your work. It's only when you realize you're doing it that you can begin to turn it around.
I can relate to this. Often I'll be in that same situation and 90% of the time I say its bad because I know it can be better. That and the image I have in my head is never quite the same as what goes down on paper. I found It doesn't seem as bad to me if I don't think about something for too long (or at all) before I draw something.
Its weird, I can spend an hour drawing something and hate it but spend thirty seconds on a doodle and really like it because I don't have this perfect expectation for how it will look.
