Just calm down
It's normal to be in stress at times of exams
Focus on studying then on results
Self study is most important
You can try the 20/80 rule. Figure out the 20% most important things in your syllabus and spend 80% of your time studying that. Do check out previous question papers- very very important often times the questions repeat. Try to understand all the concepts by heart. And remember you don't have to meet anyone's expectations. Marks don't matter much once you're out of school. Its always more important to be a good human being, develop your overall personality than to get high marks. All the best.
Don't study for anyone else but yourself. Relaxing is important as well. Set some goals like I'll have a chocolate after I complete chapter 7, reward yourself for hard work. Another thing is don't think about expectations and other stuff, just concentrate on your study material