When is it Time to Hang it Up on Extreme Sports?

What about not surrendering to "Father Time"? The idea of this rather unusual amalgamation was to hike up into rocky, backwoods terrain after a good size winter snow fall and climb up some hill and ski back down using the natural fall line over fallen trees, stumps, rocks, ravines and deadfalls. The skis had to stay on. At what point do you stop racing cars and motorcycles? Quit jumping out of airplanes? Hang gliding? Mogul skiing? Downhill racing? Surfing? Mountain climbing? Sky diving? Now in my case, I was forced to give that question some serious consideration when while engaged in my favorite ski/climbing sport I tumbled fifteen feet down a ravine and tore up both knees. Wasn't it time to come to terms with reality?