I agree with jessica. People discount the mind-body connection, but getting moving can work wonders on your ability to concentrate. Be sure to eat high protein and low fat around the times you need to be at your peak. Another reason for low-energy is dehydration, which coffee makes worse. Drink water. Stay away from diet drinks because they inhibit your concentration by suppressing the electrical impulses in your brain, temporarily, but not good when you need to be concentrating!