Two things I did today where I stopped and realized, "Oh jeez, I'm a loser."
1. I was walking down the street, and it was very muggy, so I pulled out one of those Japanese fan things and started fanning myself, and then realized, "I probably look like some some southern girl at a debutant ball." I quickly stopped.
...and 2. I was at the gym, walking along, when George Michael came on the radio, and I kinda started bopping along to it. Again, I quickly stopped myself.