if I was a doctor and could give you advices on how to get better, I wouldnt be posting on this site anymore.
but basically, you can go find stuff on how to prevent yourself from being in a bad condition right before the exams. there are loads on Chinese websites but i dont suppose this information will help most of the people visiting this site.
I looked for and translated some of the before exam tips for one of my friends who was freaking out a couple of days ago, I will just post what I can remember, its all pretty much common sense:
1. dont eat too much oily stuff, and make sure that you are not 100% full after meals, recommended: 80% full.
2. watch your fingers as you shut doors, windows etc, especially the hand you hold your pen with.
3. DONT HAVE ANY SLEEP DEBTS, cos you cant pay them back the night before the exams
4. avoid listening to music, especially new music, cos they wont help you concentrate
5. avoid anything too exciting before the exams, cos anti-climax will work against you making exams seem longer and harder to take.
cant remember anymore, hope that helped.