Sleep! Sleep is not for wimps, no matter how much people talk about pushing through. A dream can also give you a present to get out of block or a story problem.
Going short on sleep even a few days is an open invitation to any cold virus or other bug to come for a long stay. When sick, writing will be twice as bad and often be pure junk. Four hours in early November cost more like fifteen when the deadline is looming.
Don’t do it! Sleep at least an hour less than your usual. But I’m beginning to think even that is counterptoductive.
My NaNo cold came early this year.