I spent more than 20 years racing motorcycles - Formula1, Superbike, 250cc GP, 100 to 1100cc Production bikes and having won 4 amateur championships and dozens of races I finally retired at age 45. This was after a string of 14 race weekends either winning or finishing on the podium. When that streak was finally broken (after nearly 3 years) I just did not have any more competitive juices left. Still don't even now at age 63. I ride to enjoy the outdoors - both mountain biking and some road and bike paths - and almost always feel better about the day after riding. I do enjoy watching some of the local races (enjoyed round 1 of the GA cyclocross series this past weekend) but I don't think I'll ever ride for personal bests or pin on a number in a race. So, I know my limits are only mental but that is where I'm at now....