One of the best ways to revise for a maths exam is to practise past papers. This way you’re exposed to the full maths syllabus and become familiar with the types of questions and how these are presented.
Work through the paper, show all your working, and check and mark your response against the mark scheme. If you got the question wrong, try and work out how to get the correct answer. If any areas of weakness become apparent, go back to your notebooks and textbooks and review the topic. If you’re still stuck, ask for help.
Work through as many past papers as you can, following this technique, and you should feel better prepared and therefore more relaxed during the exam.