I really like these two quotes: 

One of the biggest, and possibly the biggest, obstacle to becoming a writer... is learning to live with the fact that the wonderful story in your head is infinitely better, truer, more moving, more fascinating, more perceptive, that anything you're going to manage to get down on paper. -Robin McKinley

70 percent of what we do [writing] involves staring into space trying to figure out what the hell is going to happen next. -Robert Gregory Browne