Story/Plot is by far my biggest insecurity/overthink fodder. My writing skills aren't nearly as developed as my drawing skills, so I'm always worrying about if a story's too generic, if I'm telling it poorly, and especially finding myself writing plot holes/leaps in logic somewhat frequently and stressing over how badly said instances are ruining the overall story. Not that bad, probably, but I still worry xD
The writing, and the way dialogue is phrased. I often worry that dialogue doesn't feel natural, and sometimes I rewrite the same thing for a very long time until it feels right. There's also a couple of plot holes in my story that need to be taken care of. 
Sometimes I overthink about the scenes I made like, in the last episode one of the characters forgot to pick the key of another character's house, so they had to pick from the character's pocket
Then I overthinked again for overthinking if it was too stupid to add that, even thought I've never showed the character having the key of the another character's house lmao, and started thinking "Will readers notice that if I don't show this scene?" aaaaaa
Anyway, the lasts episodes from the arc I'm working on is too complex and I have to be extra careful to not add something not related to the story itself, otherwise it will influenced the ending of the series. The next episode is the last episode before the last arc too omg
tbh all my shading layers, i need to change how i color my pages because the way i do shading layers makes it hard to do dramatic/special lighting but i feel like i cant change it at this point.
I harp on the dumbest details- whether they are realistic or not. Like I picked some jobs for my characters' parents. And then I harp on whether or not those jobs make sense with their presented wealth. SO for example the main girl in my story has a mom who is a well off lawyer, and a dad who is a principle software developer... I then harp on things like- estimating their yearly salary, then assuming the type of house they would have in the type of neighborhood they'd have, and if they are making enough for that? What would be their take home income after taxes and mortage... I know the comic is set int he Seattle area, what is the average cost of living given the type of car, type of house, type of lifestyle they have, healthcare costs, etc etc for a 4 person family... it GOES ON AND ON AND ON. I have a problem. Yes I did this for all my characters and their families. And near none of this information is presented in the story.
AAAAAaaaaah, DIALOGUE. It's one of those things where your goal is to make it as natural as possible, so if you keep working at it for a long time, it'll start sounding more and more artificial. My tip is to listen to videos or observe people when they talk. Just find a Youtube video and listen to people have conversations.
Dialogue and how to include foreshadowing without being too obvious.
Also I struggle how to explain stuff without making it an info dump. I take the advice of a post I saw once which said to act like your readers are already familiar with the world and characters to avoid info dumping. Of course the post was about fanfic but it was mentioned cuz since it’s fanfic you can skip introducing the characters in great detail.
Like you don’t even learn the last names of my characters until chapter 3. Honestly you don’t even know the name of the cat familiar (or even that he is a familiar) until later. I think I’m working that into chapter 4.
As far as dialogue goes I suppose I have the benefit of being born and raised in Texas and I’ve just decided that my stories are all set in Texas unless otherwise stated... so I’ve got a lot of slang I can utilize.
Anyway so it’s mostly the writing part I struggle with. The art, I usually struggle with props or detailed rooms or things like trains / cars / etc. Which sucks. Also perspective, particularly in the case of bedrooms. Mostly cuz I draw traditionally so I can’t zoom in to get all the details and still get the perspective right. But I try to figure it out somehow.
Gods! I'm always stuck on inventing terms for things, names for places, and fantastical slang words. I swear I spent HOURS trying to come up with a slang term for a race of beings in my fantasy realm...
Definitely the writing, but mostly with like... the inconsequential details, haha. Is this piece of dialogue too out of character? Does this dialogue convey something I don't want to convey? Is this real-world detail actually factually correct?? Maybe I should look it up for the 12th time...
I feel this so much! The thing for me drawing my comic traditionally too is like... trying to get the vanishing points placed well. Typically you want the points off the page for 2 and 3 point, but my drawing area's just not that big (maybe 2ftx3ft, drawing on 11x17 paper) so that's frequently a challenge xD I'm not that good at faking it yet either, so you can definitely tell the panels where I start start trying to and the perspective starts looking really off lmao
Composition- of individual panels, my pages, and how the pages need to fit within a certain scheme of what I'm doing.
Time
I always compare my output to others. Like comics take me months and writing also. Like I wish I could just crank out a couple chapters a week, but that's impossible for me.
I wish I was better at producing and making more. I hate having gaps where there's no content for a while -- if I was a sub it would irritate me.
Every. Single. Time. Ill have a scene written for a story and then i look at it like "this makes no sense, no one would get this but me" So then i revise several times until it is so dumbed down that it would probably insult readers intelligence so I bump it up a few notches as continue in a self destructive cycle.
If it makes you feel better, I bet some of them have big old buffers and thats how they can do it. Some comics even have several people doing the writing, drawing, and coloring.
If people can overlook a whole DAMN OUTFIT SWITCHING COLOR IN THE MIDDLE OF A SCENE then I don't think you should worry so much about a spot, but the things I overthink the most in art is the quality of the image and if my art is ugly and the panel placement. As for the writing I always fear someone won't interpret it the way I intend the story to be interpreted and that there might be unfortunate implications.
I see that we're all different drops in the ocean of horrible creation worries XD
Honestly reading these kind of...soothes my own worries a bit.
plotholess,, for sure
i always end up thinking of "but what if" scenarios no one else really cares about (or ever, ever asks about)
which can sometimes honestly trip me over and often delays my work
but in terms of art im the exact opposite, very straightforward pen-to-page no-thinking process, so its interesting seeing how many people get tripped over that!
