I was paranoid all day, convinced that what I wrote (and what I write) is crap, but I had a good day at work and a good night at home. What I've realized is that I'm a writer.
Will something good come from yesterday? Don't know -- and it doesn't matter. Sure, I write because I want to publish, but I also write because it's a part of my identity. Reading is fine, and I receive a great deal of enjoyment from that aspect, but there's a part of my brain that wants to tell stories. Now, it also tells me I've got a long ways to go before I can string together words like some of the people I read; that's the paranoid side of the equation.
Here's the secret, though. You're never good enough. I think that's why Wolfe's comment about learning to write novels rings true for me. We're gods when we write. Flawed gods, creating worlds where nouns and verbs carry the weight of action, and things don't always turn out the way we want. There's always room for improvement in your work, and you either see that as a burden or as a challenge.
Do I still need to work on yesterday's submission? Sure as hell I do. I want to please my own sense of accomplishment and I want to please the person who requested it. I'm a good boy that way. Everything I learn writing one book or one story goes into the next book or next story.
Because I'm a writer.