Deep breathing can help. If you feel overwhelmed at the sheer amount of studying that needs to be done before the exam, stop. Now find a quiet place. Sit up straight. Breath in deeply and count to five, pause for five and now exhale for five. Keep repeating this for two to three minutes. This can calm you down and will help you think clearly. You will now be able to work more effectively.
Even the smallest amount of exercise can boost productivity, confidence...