This is valuable time, yet probably the easiest to waste. Get into the habit of using it productively. Do not schedule time for certain things, such as studying, when you know it is impractical. We all have a time of the day when we aren't likely to accomplish much. Plan for a good balance of activities.
College life has many aspects that are all important to success.
Accomplish a few vital goals rather than many trivial ones. Break large, overwhelming goals down into smaller, more attainable tasks. Carry a pocket planner or datebook. Keep a semester calendar. Do unpleasant tasks first.