Many years ago I was a really decent runner. Before a big race, I would get my hair cut. I felt lighter and more aerodynamic.
The days when get a haircut I have this reverse Pavlovian response. After a haircut, I want to go for a run. I also dig deep for a far flinging kill two stones with one bird approach (sic) . I need a shower anyways so why not go get sweaty.
The Side Effects of Endorphins 