"I no longer thing of it as block.-Anne Lamott, from her chapter "Writer's Block", pg. 176-182 in the brilliant Bird by Bird: Some Instructions on Writing and Life.
... The word block suggests that you are constipated or stuck, when the truth is that you're empty.
...If you accept the reality that you have been given--that you are not in a productive creative period--you free yourself to begin filling up again.
I encourage my students at times like these to get one page of anything written, three hundred words of memories or dreams or stream of consciousness on how much they hate writing--just for the hell of it, just to keep their fingers from becoming too arthritic, just because they have made a committment to try to write three hundred words every day. Then, on bad days and weeks, let things go at that.
...Everything you need is in your head and memories, in all that your senses provide, in all that you've seen and thought and absorbed. There in your unconscious, where the real creation goes on, is the little kid or the Dr. Seuss creature in the cellar, arranging and stitching things together. When this being is ready to hand things up to you, to give you the paragraph or a sudden move one character makes that will change the whole course of your novel, you will be entrusted with it. So, in the meantime, while the tailor is working, you might as well go get some fresh air. Do your three hundred words, and then go for a walk. Otherwise you'll want to sit there and try to contribute, and this will only get in the way. Your unconscious can't work when you are breathing down its neck. You'll sit there going, "Are you done in there yet, are you done in there yet?" But it is trying to tell you nicely, "Shut up and go away."