College students who don't get adequate sleep on weekends have been found to forget up to 30 percent of the material they've learned during the previous week, even if they spent plenty of time hitting the books [source: Gardner]. Positive sleep habits can help improve memory and sharpen focus, especially if you're learning something new [source: Sparacino].
If you could benefit from better (or more) sleep, make a few simple changes in the weeks leading up to your GRE. Establish a bedtime ritual that helps you wind down, such as listening to music or taking a warm bath. If your mind continues to race, writing down your thoughts can help you relax. Turn off the TV and stay off the Internet; electronics stimulate the brain and you'll wind up needing extra time to fall asleep. Train your body when to go to sleep -- and when to wake up -- by sticking to the same timeline every evening and morning [source: Mayo Clinic].