Tuesdays are often my most productive day. It's the beginning of the week, so I still have energy and motivation left. I don't have class. I don't play basketball at noon like I do on Mondays and Fridays, and I only have one longstanding commitment, my office hours. But since my students never come to see me, the whole day is basically free to devote to actual work.

I made the mistake of going to check my department mailbox. In there, I found some papers to grade. No big deal, I thought, I can get this done in less than an hour. On the way back to my office, I ran into the professor for whom I am a TA. He asked me if I could come to his classes all day to "proctor" (babysit) the exams he was giving out in 15 minutes. And there went productivity.

The lesson? Never leave your office.