Now that I've put in a few words for NaNoWriMo, there may be people going "Aaah! I can't do 500 words, let alone 50,000!!" No problemo! Not everyone writes in big bursts; many don't write steadily, or at great speed.
Anthony Trollope said: "Three hours a day will produce as much as a man ought to write." But Anne Bernays thought it was "shameful" that on her best days she wrote only about three or four hours. Samuel R. Delany, who is pretty severely dyslexic, once proclaimed himself very pleased for writing a "perfectly wonderful sentence in only twenty minutes!" For some people, slow and steady wins their race.
I met a woman once who was terrified of writing. I mean in the sense of provoking anxiety attacks. But she had a doctoral dissertation to write--a long one--and trust me folks, it takes a lot of writing!
So she set herself a goal of one sentence a day. She didn't have to stop there, and often she wrote more, but that was as much as she could face. I think of this as the terror of the blank page--going from nothing to something is harder than something to something more, for some people.
I've said elsewhere that people set too high a standard for being creative; I think this applies here. Just starting makes some people second-guess themselves, because suddenly they must be creators. This is, I think, one reason why a lot of people like fan fiction--they don't have to create the world from scratch. It's a smaller scale of creation, and thus less intimidating, though still satisfying.
I think I've said this on the LJ before, but it's worth repeating. If you wrote only 200 words a day (2-3 good-sized paragraphs), you would have a novel's worth of words in a year--over 72,000 words!
The trick is setting the goal that energizes you--or reassures you that you can probably do it. 200 is way too low for some people; writing every day may be too stringent a standard; 200 may be too high for you. Whatever works!