The Pomodoro technique is according to Barbara Oakley one of the best studying technique. The technique says that you have to work intensely in 25 min without destruction’s, followed by a rewording. The reword does not have to be a treat, it could be anything from a walk to a Youtube video.
Barbara Oakley does also have a technique if you have “hit a learning wall”. She says that you have to stop working. That will turn on a part of your brain that is not active when we are concentrating. According to miss Oakley, the brain will if you are working on a math question that you do not understand. Work on the problem while you are resting, and when you come back it will be easier.