In the past I had a tendency to wallow in my depressions. I would get one negative thought and let it carry me to the next one and the next, digging a hole ever deeper and more difficult to climb out of.

I have two favorite kinds of negative thoughts: self-flagellations and paranoia. “You should have said this,” or “You should have done that.” I go over and over past actions, reminding myself how I have screwed things up yet again. Then for the paranoia, I think about the fact...