That's a toughy-- I have the same problem. Have been getting by (barely) on 3-4 hrs sleep a night for months.
A lot of people here suggest exhausting yourself physically, so that you'll just conk out when you fall into bed. The trick, i gather, is to do it earlier in the day, because you'll only rev yourself up if you exercise right before bedtime.
I need to do this myself, but it's hard to be consistent about exercise when you're so tired (vicious cycle).
Something Eckhard Tolle suggests that sometimes helps me is to concentrate on my breathing for a few minutes-- be mindful of your breathing and nothing else. It interrupts the train of obsessive thought, at least for it bit.
