I'm currently a graduate student in engineering (working toward my Master's). Over the summer semester I'm taking three classes in addition to researching at my adviser's lab.
The lab is located off-campus (about a 30 minute commute), so it doesn't make much sense to fill in all of my gaps between classes with research time.
However, after making my schedule, I realize that I have these awkward 2-hour breaks in the afternoon. I also have 30-minute breaks later in the day, as well.
Given that I can't research in these times (the commute is too long), and given that I'm generally a nocturnal person and like to work on problem sets at night (from the comfort of my dorm), what is the best academic use of my time during these breaks?