If I get to the point to that the studying is overwhelming or it is not working, I try to change it by trying to look at it differently: talking about it with someone, studying with others, looking for other resources on the computer or at the library, changing how I study.. if reading, then writing somethings out or using the computer to do it, reading out loud, etc. Anything to change up the routine. Besides also using the outside interests as the breaks in between so I have time to digest the material; never underestimate breaks and distractions. Find a new distraction to change things up. Sometimes I actually get more done in the breaks mulling it over to help with my retention than during the reading and problem solving sessions themselves.