Perhaps it has something to do with the imposter syndrome[0]. Feeling like you're not a "real" programmer who doesn't "deserve" to have the position you do would (I'd wager) cause that phenomenon of analysis paralysis; it would cause us to want to get it right or we'd be "found out" for the "frauds" we are.
I hate it, and I've found personally using the techniques like Pomodoro[1] has helped immensely with just doing something! along with TDD coupled with exploratory programming.
How does everyone else deal with it?