One problem, which I think should be the topic of someone's grad thesis, is the directly proportional relationship between studying and snacking. The more I study, the more I get the munchies. And it's not a matter of being hungry at all - I just desperately crave tastiness in my mouth. (This is a very slippery slope.) For example, last night I inhaled a bagel - didn't bother toasting it or anything. And between lectures, I feel a strong need to eat something. So I usually do - but I think I'm going to put an end to this starting tomorrow.
Also, studying takes a lot out of me. I'm getting 8 hours of sleep a night, and I feel I could use even more. I figure my brain is requiring extra cataloguing and info-absorption time, and so far, I've been happy to oblige.