It's very easy to fall into the trap of treating study like a part-time job; clock on and clock off. The difference is, while you might get paid for your time in a part-time job, your time investment with study simply does not pay off. If you study for 3 hours, does that mean you earned yourself 3 hours worth of marks on your final exam? Not necessarily. The quality of your work will be the important factor. Did you spend 3 hours staring at a blank page while watching Youtube videos or did you do a practice exam?
Remember, when you sit down to study, make yourself a list of core tasks that will help you prepare for exams. Remember, measure your progress in terms of tasks, not time.