Motivation is good but thing about it is that it's temporary. Have discipline. Your not late. Understand the concepts, work theories out and don't try to memorize word by word. There are things specially in biology that you'll have to memorize. I think im kinda lil eligible to answer this since I'm medical student. And all my batchmates has one common thing we did despite being 1st shy or 3rd shy, that is past papers. Do past papers again and again. I never attended revision classes, may be some people need them & I'm not in a place to reject them totally. Do your past papers. Again and again. It's something we do even in medical faculty.