Personally, if I were in your situation, I would find something that makes you happy and do that as well as revising. Try revising in a place outside with a veiw. This may calm your nerves. Try sucking a mint while your revising and before the exam. This may help you keep calm. Does this help at all or would you like me to go into more detail?
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Admin. Creator, Keeper and helper to all. I hope this helps you.