Many good tips given by the community but I’d like to introduce the concept of diminishing value of returns (for studying).
At some point in time, you’ll find that an extra hour put into studying will not yield the same results. For eg, your first hour of studying will get you a C grade then your second and third hours of studying will get you a B grade. But to get an A, maybe you need an extra 5 hours of studying.
This is where you need to determine which generates most returns and satisfaction for you - 5 hours to move from a grade B to A or 5 hours with your friends and family?
I personally try to find that equilibrium in everything I do and maximize my time investment.