I always get tensed before exams, i tend to forget things and my palms sweat a lot.what do i do?

Practice a: Technique called the relaxation response. It's simple and outlined in a book by herbert benson. You need to re-train your autonomic nervous system, the part of it that gets the fight flight freeze response activated.

Breath ; relax: Breath in slowly ; deeply through your nostrils. Fill your lungs with air (but not to the point of discomfort). Hold for a count of five then slowly begin to exhale through an open mouth. Repeat at least 12 times, longer if you need to.