[color=crimson][b]For myself[/b], I find the hardest part of roleplaying is, as [@Fillet] and [@Mr Allen J] have pointed out, is writing. It's hard for me sometimes to find the inspiration to write a long-ass post and even harder to be able to put it to words. Like Fillet, I, too, am a visual person. I like to envision what I'm writing - sometimes by physically doing it myself - and try to put it to words, but I also can find myself in the difficult position of not being able to get it out the way I had hoped. Sometimes it comes out longer than I envisioned. Oppositely, it can come out shorter than I had envisioned.  There are varying factors that apply, but sometimes I just can't get it out. I often blame that on writer's block. XD

[b]For rps themselves[/b], I think the hardest part is definitely keeping interest both as a GM and as a player. If the rp is going slow - and I mean really slow. Like, think only one post per week. If that's the case, my inner-morale that keeps me into/out of a certain roleplay goes to a severely low level. If it gets too low, I tend to just drop the rp like a hot potato. As a GM, I really try to keep people interested, but one can't really do anything if people won't make the effort to post, right? Sometimes one simply has to abandon the sinking ship.[/color]