A few days ago, someone asked me what I do when I'm experiencing writer's block, and Earnest Hemingway's famous quote, "Write drunk, edit sober" came to my mind. I've never taken this quote to mean that you should be inebriated before you sit down to write. Hemingway was known to be a heavy drinker, so it is possible that he meant it literally - although there is much dispute about the validity of a literal interpretation among Hemingway experts. After all, it would seem quite foolish to take the quote as serious advice if it is literal. In fact, it has never be confirmed that Hemingway actually even said this, and it's likely that the words can be attributed to someone else. (See Jeff Goin's article for more on this)
Regardless of who made the statement, I've always thought of it as a hyperbolic way to demonstrate the distinction between writing and editing. When you write, you should approach the work with enthusiasm and energy, without being too critical. It's sort of like how the Greeks used to talk about calling on the muses for inspiration. It's a different state of mind.
Creativity needs spontaneity, so you can't take the time to filter things out. You've just got to get it all down. After you've put it all on paper, you can step away from the writing for a few hours or a few days and then come back to the work refreshed - sober minded, as it were - to begin viewing it in a more critical light. This is the editing phase, where you take out the bad, identify the good, and add what is lacking.
That's how I overcome writers block: I just sit down and write, but worry about accuracy and style later. Writing "drunk" (again, I use the word figuratively) will free you from the paralyzing fear of failure and allow you to release all of your ideas.
Keep this distinction between writing and editing in mind, because it just might help the next time you find yourself battling a tough case of writer's block.