[A2A] I answered a similar question a couple of days back: Brijesh Kumar's answer to How should I improve my performance during an exam?
The essence is not to give undue importance to these exams. Even if you do badly in an exam, you will still live, your family will still be there, your friends will still be there. In the grand scheme of things (if the goal is to be happy), these exams are not that important. This does not mean that you should not study. Study, to learn, not to write an exam. The exam will automatically go well if you know the subject (which is possible by regular study, not by day before exam study) and you don't give undue importance to the exam.