For me its 100% pacing. A scene which would normally take a minute to read on the page takes six months to publish on site and its just not fast enough, and getting that sweet spot of 'what's important and what's the best way to show that' with a ""controlled"" pace is my biggest problem.
For me it's definitely keeping to a schedule/having motivation. I can power through art and writing, but oftentimes that deadline comes up and I realize I haven't done nearly as much work as I should have. I run out of buffers really quickly, lol.
I think long-term story planning was probably the most challenging thing for me on this comic!! I'd previously done a couple of other comics, but for one of them I worked with a writer, and the other was more of a goofy autobio, so Runewriters is the first comic where I had to write and manage a longform story. Keeping all the different threads of story and different arcs of character development straight and figuring out the best places to seamlessly drop exposition and how far in advance to start setting things up so that they're meaningful when they finally happen -- all this stuff is super interesting to me but it was a HUGE learning curve when I first got started.
That, and use of colour. Creating more interesting colour palettes with my pages is something I'm working on improving!
Perosnally, I struggle the most with backgrounds and making them look nice. I drew an apartment and forgot to put windows in the living room. The layout of the main character's house also makes no sense and is also missing windows....which I didn't notice until later. Oops.
Something that I see some newbies struggle with is the concept of visual storytelling. Like having varied composition (beyond medium shots of characters plastered in the middle), having characters emote with their dialogue, and having the narrative flow.
thinking what comes next after pages after pages also which clothes suit the characters and the intimate scenes that's tough because you know...
hmmm...
maybe juggling everything? simultaneously staying aware of gesture, and form, and composition while drawing. its easy to accidentally make my drawings flat because im focusing on making the page flow - but thats mainly because a lot of these concepts are fairly new to me.
Hmm. Perspective is still giving me a nice challenge. Specifically when it comes to drawing my characters in the environment, and making sure everything is scaled correctly. I'll get it though! 
For me I say storytelling in general. It is making sure I pick a good number of panels, they are clear and interesting to look at, that the shots tell the story well. Most importantly can the reader tell what is happening? I feel like I fight with every new page.
1) multiple objects and people in one panel. Keeping perspective consistent
2) character consistency. Things like hair length, eye color, accessories like belt buckles, earrings, rings, etc. Pay attention to detail!!!
Drawing big. I've always been someone who drew really small, filling up regular sized pieces of paper with doodles upon doodles. It was really hard for me to draw large, especially when I made the shift to digital art. But I knew that I wanted to print my comic therefore it needed to be a print-ready size. So I had to draw the picture on a larger scale. Now this is no problem to me, but it's the reason the first page of my comic is slightly narrower than succeeding pages.
Planning out a story in a way that makes sense and like... writing in general. I think I'm a pretty shitty writer, but I like writing so whatever I guess.
Then again I think I'm a pretty meh artist too. ヘ（。□°）ヘ I guess all I can really take pride in is my update speed. Derp.
Pretty much everything to do with promoting.
You can argue that that is not a skill, but yeah... it is and it takes a a hell of a lot of time I would rather be drawing or writing with =/
Probably the hardest thing for me is pacing. This would be my first attempt at a webcomic with a longer story and I've definitely had to go back and think about whether or not some smaller scenes are necessary.
That, and keeping a consistent schedule. I've been all over the place.
I'd say for me it's the coloring. I guess I could get away with black-and-white cartoons (which definitely have their own unique charm), but one day I just started coloring and coloring, and now I try to color anything that's going to get posted. It's just rather tedious for me, and that's probably the hardest aspect of creating my webcomic.
i can't speak for candel, but for me personally i have a really hard time with pacing
if you let me run loose by myself i'll draw a panel for EVERY change in expression and eVERY nonverbal tic, because i tend to think of comic planning more like storyboarding an animatic when they're two very different mediums
-goji
I agree, colouring is the most challenging. Mind you I am only just starting posting my comic Real Dreams2, so I have a lot to learn
I have yet to post my comic yet, but while working on it I realized I have difficulties with keeping the background from competing with the foreground. It's hard to keep the bg colors and toned done without it looking gloomy and sloppy.
Seconding this. I have the big-picture plot and even scenes of the comic outlined, but paneling them in a way that makes the story flow easily, with pauses and emphasis where important, while keeping the panel layouts varied (so I haven't drawn the same character's face in profile 3 times in the last 2 pages) and making sure speech bubble placement makes sense... that's hard.
(part of the struggle for me is that I watch a lot more animation/movies than I read comics, so I tend to panel things as if they would be appearing in animated format, and sometimes that doesn't translate exactly to a comic.)
Man I getchu on that but I feel the best way to overcome this is just to accept your finished page and done and over with instead of nitpicking on the shapes. Trust me, it's the worst.
I think the main difficulty I face is motivation lmao I want to give up on my comic very often and it's rather difficult to tell myself I'm doing okay enough to draw through it.
Backgrounds are the worst.
Judge me3
I find it fascinating that so many are having problems with panelling and deciding how to actually draw their stuff... For me the problem is opposite. Panelling and drawing is super easy, and a quick fix. Actually planning scripts in a way that makes sense and doesn't make me want to puke on whatever I wrote just so I can't ever read it again, on the other hand, is bloody difficult.
