Although you can not control other people's actions, you can control your response. Set up and maintain good study habits. Get prepared for tests and paper throughout the course, don't cram. Learn to relax. Dont' suppress having a good cry.
Tears can help cleanse the body of substances that form under stress.
Count to 10 when you are upset. This gives you time to reflect on what's bothering you and helps you calm down. View changes as positive challenges. Don't get down on yourself if you don't do well on a test. Plan to be better prepared next time.