Try to get enough sleep tonight but don't worry about it if you are lying in bed having trouble falling asleep. Studies have shown that lack of sleep the night before and exam doesn't effect your performance on multiple choice questions, and the written part doesn't really matter anyways. Try to be in bed by your normal bed time, and if you can't fall asleep within an hour or two, you might get up, watch some TV for 30 minutes, then try to fall asleep again. Studies have also shown that counting sheep is not as effective as imagining yourself in some scenic, empty location. Of course the best way to fall asleep is to empty your mind, but if that's not possible, you might picture yourself out by a waterfall or something. Good luck!