This year I had an entire class about the psychology of learning.
What I gathered that helps is not focusing so much on repeating the content over and over again, that is a part of some classes but after you know a concept make questions about it and see if you can answer.
It is all about focusing on understanding what is in front of you!
Another thing that is very important is self-discipline, knowing when it's study time and non-study time, mark on your planner or calendar (I use a random online one), which includes having some places to study and others to decompress. One thing which really helps me, in particular, is the Pomodoro method (my teacher doesn't like it hehe), if you have more difficulty in getting yourself concentrate you can try expanding the Pomodoro from 25 to 50 minutes.
I realize I wrote too much... Bye-bye, stay hydrated and make pauses, without pauses my brain would explode.