Hahaha, it's funny cause I often experienced that xD At the end of a semester, we have exams for all the objects we make and the exams are held like 2 days (more if we are lucky) distance one from another xD So it's not really time to study so sometimes you usually go overboard sleeping at 3 AM or 4 AM and waking at 9 AM or so (in time for exam) or sleeping at 11:30 pm and waking up at 4 AM xD (I usually prefer the second one cause I don't drink coffee so it's kinda hard for me to stay until 3/4 AM, but if I am really desperate.....). SO, yeah, I have experience xD I am usually so sleepy after that and my brain is malfunctioning getting headaches and all (I am prone to them by now, me and headaches are best "friends" XDD). If I can, I take a nap and it helps a bit....if the headaches don't go away then I take some painkillers too. Well, it's only natural for the body to react that way after all, more if you are kinda sensitive one (like me). But there are people and people, you either are too tired from the start (like me) or either be the most active person starting singing and all (like some of my friends) for a short period. Either way, your brain and body will feel tired in the end xD