A friend of mine once told me that a nurse taught her this trick when she was in the hospital as a kid, and it if you're desperate this might just be crazy enough to work is to systematicly trying to tense up your muscles, starting with your toes, and go up and hold the tension, and then suddenly release and relax... I tried it and I swear if you can manage to really tense up and hold EVERYTHING (which takes quite some effort) and then suddenly relax its like you get a major headrush and I actually fell right asleep after it. Once.