Three hours is a lot for a day's intense work. You don't "work" that hard when you are at school. I hope you broke it up in bits of 45 minutes or so and did other things inbetween?

Pretend the revising is class/tutoring and "go to lunch", back to your quarters, etc. LOL. Mix it up.

It's early yet, I'm sure you'll be more than adequately prepared. At first it seems a lot and like you'll never get it learned but it gets easier as you cram more stuff in, LOL. Have fun with the material and be imaginative about it; write yourself little poems and ditties and try to make two things with no connection to one another have a connection. Just the thinking about it, even when you're doing something else, will get it remembered so when you actually are in the exams you can smile the whole time because you'll be thinking about the physics of flowers when you're doing your maths.

If it feels like you're going to do poorly anyway, then at least enjoy it? Get fatalistic about it that way; have a good time studying if you're going to study at all. Have a good time doing the exam. Who knows how you'll do? You're studying as well as you can, you've passed exams before, etc. Might as well feel excited and challenged by them and see what you can learn, what you know, as be feeling anxious and defeated?