College was the easiest period in my life to maintain training consistency, second easiest was medical school. The only time mental stress got out of control was once when I had been sick and was skipping the gym. I echo what has been said above, schedule your gym time like any class. Jog between classes and use the 10 minutes you save crossing campus to study. Breaking a block of study time in half with training can be a good way to improve your concentration. Beer will still exist when you graduate, you will never be in your early twenties with access to a university strength training facility again.