pump up the pain

I was thinking about how we take for granted having no pain day-to-day for the most part.  I realize that not every young or middle-aged person is completely pain-free, but for the most part, we move and shake pretty easily until we get up there in years. Older people clearly look like every step takes a major effort, like my father trying to tackle the bleachers at Jonathan's basketball games.  I cringe when I watch.  So then I have to wonder, why the heck do I inflict pain on myself willingly by taking the grueling power-sculpt class, or boot camp session or boxing workout and pushing myself to the limits?  And it's not enough that it hurts during the class itself, it really does, but for the following 2 days, every single step is wrought with pure pain and muscle ache!!  I must be trying to punish myself for something, but I can't think of why I would want to do this do myself willingly when only a few days earlier, I was hustling along happy as a pain-free clam.  I mean if I can see the future, I know that going up steps will someday hurt without me doing an exercise class the day before, so I surely don't need cause myself pain by choice now, right?  But as I near the end of the day 2 aftermath of the most recent muscle-shock class, I know that by tomorrow I will forget the hurt and in a few days the new some-cool-name class will draw me in because it sounds like such a great way to stay in shape and ouch, "no pain no gain" - the vicious cycle continues...