I'm having one of those writing days where I feel like every word I write is stupid and nothing comes easily. It's only annoying because I haven't had much time to write this weekend, since I worked both Saturday and Sunday.
When I have days like this, I always remember back to the interview I did with Neil Gaiman for Science Fiction Chronicle back in god-knows-how-long-ago. He talked about that classic idea that really, showing up is the biggest part of writing, but his contribution to that old saw was that it's worth the effort. At the end of a novel or story or whatever, for the most part you can't really tell the difference in the writing between the days when every word was like squeezing blood from a turnip and the ones where you felt like the Muse dribbled gold out each finger. So, you know, the difference between someone who writes and someone who doesn't, is that the writer just keeps banging away, even when it's hard. (That's the gist of it, except, of course, he said it cleverer.)
Also, I take comfort that someone like Neil Gaiman has had shit-for-writing days, too.