Sitting at my boss's desk

Why do I always get to work so early? My shift today doesn't start until 3:25 and my students don't arrive until 3:50, but, for some reason that I don't understand, I felt compelled to arrive at 2:30. I call it prep time, but it always just ends up being boring Knight time. It only takes me 35 minutes to prepare for all of my classes. Why do I do this to myself?