I used to love writing. I would have no problem cranking out pages and pages of work in a short time, but over the years I've started to really dislike my writing. I'm at a point where I hate it so much that I have trouble writing simple sentences because I don't like how they turn out. I don't like the structure, the word choice, etc. And I can never think of a way to rewrite it. I can't write short stories anymore, I'm stuck on my novel, and I haven't written a single song in years. Please help me overcome this, it's becoming a huge problem and it's just getting worse. I'll appreciate any advice you can throw my way.
Honestly the only thing that helps me is to identify, in a concrete way, what *specifically* I don't like about what I'm looking at. If I can't do it in my head, I have to write it out--"I don't like this because it sounds like an oversimplification" or "something sounds off about the rhythm of the sentence" or "I don't think this undead/kobold sex scene really works, it sounds tedious and overwrought." You know. Whatever.
If I cannot identify it, I try to get other people's eyes on it to help me. This is often discouraging in itself, because maybe there's a giant pile of issues to work on. But it can also lead to the Naming of them, the numbering of things which you can then do something to solve. Maybe you don't know *how* to solve it, but you can try things. You know where to aim. The general "god I hate this whole thing" is broken down into little parts, and the littleness of the parts sometimes helps.
But sometimes it doesn't. Sometimes the entire tone, narrative, idea, plot, etc just seems awful. The thing seems irredeemable. This is when I a) walk away, or b) if I've already walked away and come back and I still hate it, I work on it in very short bursts of time. Very very short. Progress is painfully slow. Sometimes there is no progress.
Sometimes things just suck. And then I don't write.
Like lizmonster said, it has to be worth it. If you don't get anything out of it, you don't need to continue. You can always come back to it if the desire strikes.