Sialater wrote...
So... how do you convince yourself you don't suck when your inner troll is winning?
Augh, that's always the worst! I generally tell mine to go sit and spin, personally. Tell it that often enough, I've found, and you get to feeling better enough to get past the slump.
Ultimately, even though there's an audience if you put your stuff out there, writing needs to be fun for YOU, first and foremost. if you are having fun writing, it will show IN the writing, and generally other people will enjoy it as well. If you're not having fun, then you're doing it wrong.

I sympathize, though. I'm currently experimenting in a chapter of mine. I love reading humor and I'm trying to insert some into my story (need something to help show character bonding and to help break up the action/drama/angst). But I've been agonizing and re-writing it over and over. I will read it over one day and giggle myself silly. I'll read it over the next day and think, "Oh God, my story's already jumped the shark and it's only Chapter 5!" So, I'll try and finish up the experimental chapter and shoot it to my beta, who'll help me know whether I should continue my fledgling attempts at humor or not.

Honestly, having a beta helps. I have one who's been an awesome "constructive cheerleader." If I'm feeling poopy about my abilities, I will go back and re-read reviews I've gotten or, more importantly, her beta emails and pump myself up.
But mostly, you've just gotta boot the inner troll in the rear.