Start by sitting in a chair or on the floor with your back straight. Exhale and let your chin float down until it rests on your chest. Exhale and continue rolling your head over to the left and foward until it comes back to rest on your chest. Imagine you are drawing big circles on the ceiling with the top of your head, rolling your head 360 degrees around the axis of your neck. If you stop and do a couple of neck rolls every hour, you'll probably find that you remember more of what you are reading, because you'll be less tense all the way through.
Yoga postures work on the same principle as the breath.
When you're stressed, your muscles contract, your blood vessels constrict, your immune system weakens, and your digestion is thrown out of whack. As a result, you feel anxious and depressed, in other words, just plain bad. When you move in yoga postures, all the systems of your body are stimulated. Your circulatory system brings more nutrients to your cells and removes more waste, your lymph system fights infections better, your muscles are lengthened and relaxed, and your metabolism is given a boost. You wind up feeling healthier, less stressed, and more connected to yourself.