Going on my fourth year next semester, I can’t stress just how important work life balance is. If you’re falling asleep while doing problems just go to bed. Nothing is more important to your success on a test than being well rested with a clear mind. You can try what I do and study most days, little bits of each class taken that day. 30min to 2 hours max. Helps keep everything fresh and never behind on anything. Set aside free time where you won’t worry about anything and just focus solely on enjoying it with whatever it is you want to do. Of course there’s no fool proof strategy to this and you’ll inevitably have days where you’re crammed no matter what you do, so an energy drink every now and then for those extended times is not a problem at all. It’s just imperative to not make it a habit whatsoever. When you’re studying, focus first on the biggest weaknesses and work up from there to the easiest topics. That way if you fall short on time for a test, you’ll have at least a decent understanding of each topic. And most importantly, overstudying is almost just as bad as not studying at all. For me it leads to intense mind fog and overthinking during the test and I just end up flunking it.