I started running in highschool for health and fitness. I joined the cross-country team my last year just to commit to it. Really though, I wasn't a great runner or anything. I can do endurance: distances and long times, but I can't do speed. It was fine because our cross-country team sucked anyways. I did get a "most improved" award at the sports banquet that year which is maybe more embarrassing than anything else. I kept running afterwards, but my consistency varied. As of a year and a half ago I started a very regular routine of running then working out. It's now a natural habit. The working out more than anything though. I need to exercise to feel good, and I won't turn back now. If anything my speed has probably decreased as my strength progresses. I'm not built for running really; too short and stocky with naturally muscular legs that make my center of gravity low.
Sounds very much like what I experienced in high school.
My dad made me run track because my eldest sister was a star but her career was cut short due to a tumor in her back.
I wasn't nearly as good as she was. I ran hurdles, not very well though. I was too short to 3-step the 110 hurdles and too slow to do anything impressive on the 300. I may have received most improved also though to be quite honest. I've noticed that feel good sense before, but it doesn't come solely from one physical activity. Do you think that it comes more often as the specific exercise becomes more routine?