Never! Repeat, Never! write several pages of "drek" while dead tired, save it and go to bed. In the morning, when you read it, it might sound better than what you wrote when you were "on top" of everything. ;^))

Um, further warning to anyone to whom this has happenned. It can be a sign that you have a tendancy to overanalyze what you are doing, and need to find better ways of letting your backbrain do the writing instead of your forebrain. Seriously. It never happens to me. When I'm tired my writing goes downhill. :(