Here are some ideas: divide your study into small parts and decide how much you will do before you are allowed to eat, for example. Or when you have done a certain amount you will give yourself a reward, such as a more special drink, or a walk outside, or listen to a song you like. Maybe something like this will help. If you are a person who likes to make 'to do' lists, then make a list of what you must do before the reward/break so you can cross it off. Personally, I love being able to cross items off a to do list.