I'm not sure if it'll work for you, but the only way I managed to really study and master big subjects was slow and steady.

Study every day. It doesn't matter how long, how intense, how much material you cover. Just study every day. Sit down and look at the subject you need to study every day. If you get bored after ten minutes, do something else. But don't skip a day and say you'll make up for it by studying twice as long tomorrow. Just show up every day.