At the moment, like most students in the country i am doing end of year exams for me this means quantum mechanics, semiconductors and schrodinger.
One of my friends recently asked me "How do you fit the gym in this time of year with exams?". Most people have the misconception that the more time you spend in the gym the better the results this is not the case. To start with the first problem you will encounter is the inability to work as hard on muscles at the start of your workout so effectively you'll end up doing a half arsed job. Training for long period of time increases your chances of serious injury such as torn muscles. Lastly exercising hard for more than 45 minutes at a time increases your bodys levels of cortisol, the stress hormone, and im sure at this time of year we could all do with a little less stress.
What im getting at here is go to the gym work hard for 45 minutes enjoy yourself then forget about it till next time it'll be probably good to get your mind off things for a little while.