This might sound a little dumb, but...the hardest part about writing is the writing itself. Thinking about ideas and plotting them out in your brain is the fun, easy bit. Sitting down and forcing it into something coherent and digestible is often hard work, because there's a part of you (or a part of me, anyway) that wants to just skip from interesting scene to interesting scene, but you can't do that. You have to have transition & exposition or else it will just be a mess of nonsensical messiness. It's a little easier to get away with stuff in comics and cartoons than it is in written stories. I say this because characters can die or otherwise have horrible things happen to them in a segment of a comic or a cartoon, and then show up in the next segment perfectly fine, and no one really minds too much. You can't do that kind of madness in a written story without someone calling you on it, viciously.

Anyway. The editing process that I go through--which is the transferring of the story from my notebook into my word processor--is the most difficult part, because I agonize over everything even after I've messed with it, wondering if it's good enough for public consumption. Hoping that whoever reads doesn't think 'MAN, this fucking SUCKS.' But then again, one could also say that the day a writer is satisfied with his/her work is the day that s/he can stop. And I don't think I ever want to stop.