I've heard it said that doubt is a good thing for a writer -- that if you don't have doubts about your writing then there's probably something wrong.
There's this John Irving quote:
“If you don’t feel that you are possibly on the edge of humiliating yourself, of losing control of the whole thing, then probably what you are doing isn’t very vital. If you don’t feel like you are writing somewhat over your head, why do it? If you don’t have some doubt of your authority to tell this story, then you are not trying to tell enough.”
So that helps. But doubt can also be crippling. It can be overwhelming. And then sometimes I have doubts about my doubts.
Fellow writers (if you're out there): how do you deal with your writerly doubts?