What exam are you talking about?
But anyway I would recommend you not to stress this much about it, since bad result likely wouldn't affect your life so drastically. I think after stress will be gone your head clears and you will be able to solve the problems you struggled with because of that.
One more thing, which is crucial, in my opinion - if you understand math (you not just remember what something is, but completely understand why that is) the exam would be nothing short of a cakewalk.