Hi there,
When I was in medical school, I used this technique: I would set a simple kitchen timer for 50 minutes. When those 50 minutes were up, I would take a 10 minute break; walk around; hit the loo, get a drink etc. If something was bothering me, I would write it on an index card and think about it on my 10 minute break. I would then return to my studies refreshed and ready to concentrate. I became more efficient at learning and more relaxed. Don't forget to participate in at least 30 minutes of physical activity each day. It can be as simple as putting on your earphones and walking around the block several times. This helps you concentrate and greatly reduces stress. If you feel that you need to snack during studying, snack on cut vegetables and leave the high-fat chips alone (makes you sleepy because of all that parasympathetic stimulation). Don't use too much caffeine and keep hydrated (keep a Brita sports bottle on your desk and keep it filled). You will find that you study better and you will sleep better at night.
Good luck!
nbjmd 🙂