If past experience holds true I will probably write an hour a day—and spend eight hours a day biting my knuckle and worrying what I'm going to write about not writing.*
Often times the most difficult part of any assignment, assigned by yourself or another, is getting started. We worry that we won't be able to develop anything good. Or that our ideas have all hidden together in some far off place. So we sit there and don't do anything.
Even the best writers and artists feel this way (this video of DFW being just one example of that). But what makes them the best, what makes them productive artists, is getting over the fear. When you put pen to paper, or cursor to screen, you're reminded time and time again that this is hard—but it's not that hard.That's the key to success.
And not doing anything because you're afraid you won't have anything is the only way to prove yourself right.
*Quote comes from about 3:30 of the video.
EDIT: Somehow my brain convinced me the quote was different what it actually is, funny how brains work, As pointed out in the comments it's not about worrying WHAT you're going to write. It's worrying about not writing. That strange paralysis where you realize you haven't written anything in a week, two weeks. Worrying that you may never write again. That's a different kind of fear, but it does fit more with the headline of this article.
Sorry for the misquote.