I thought about your post since last night. It does actually make sense to me that a good long workout tends to calm me down. If the body is ramping up adrenalin, moving sugars around into the muscles, etc., then a run, a ride, a swim would depelete those.

I was in a pretty foul mood yesterday late afternoon and into the evening. I hit the gym, did a treadmill run, some weights, got on the rower, and then hit the pool to practice my freestyle. I felt a lot better emotionally when I was done. I would burst and die if I didn't have that.