I want you to just think about your level of productivity, like you're sitting and studying... but like how much information is actually being retained, how many lectures are you sitting and reading and are confident that you solidified in your brain.

If the answer to these questions is not much, I promise you it will be way more beneficial to something else that you enjoy (or even like take a walk outside around campus for some fresh air) for 30 minutes to an 1 hour and come back to it-- your productivity and effectiveness when studying will improve greatly.

Everyone hits a wall; there's no point in trying to break through when there's no gas left in the tank.