I really wish that I could get the ball rolling on my characters. I keep on writing novels about them in my head, then when I get to the roleplay, I just say "DEY HAVE CRIPPWING BURF DEFECT". At least now I have characters. I was really, really bad pretty recently. One of the other biggest things I have to work on is imagery, more specifically, not using "amazingly" and "extremely" in every single sentence.
Specifically in roleplaying, I'm afraid that I resort to ass-pulls far too often, and there was this one time when I took someone else's story and smashed it into the ground to make way for my own. Which ended in the most disgustingly anti-climactic battle ever. I'm not that bad anymore, but the ass-pulls still stay. Mainly because I have a giant infatuating with the "Superweapon Surprise" trope and am really good at rationalizing stuff.
The biggest problem I have is that I cannot write romances, EVER. I tried, like, fifteen times. The couples never spoke to each other, aside from a single quote that was there to say "We're banging".
I also need to stop going off on tangents all the time, I try to just say "He shot his pistol", but I end up describing the entire history of the pistol and its manufacturer, which eventually explains the origin of the technology and concept behind it. By the time I'm done, you forget that it's a sci-fi story and not a history textbook.