I think
ccunning makes a good point about acceptance, accepting that running (or really any kind of physical activity involving large amounts of exertion, whether it's a
little effort over a long period or
intense efforts over several short periods) sucks, and eventually embracing that suckage. There's a certain
zen moment you get in doing stuff that kind of hurts, it's a kind of suffering that sets you free, helps you stop worrying about the little stuff, lets you realize how simple life is: if you want to
make something happen, you try to do it or you do not, and it doesn't matter if it happens or not or how bad you want it to happen - what matters is that you gave enough of a fuck to try, and that you got an answer when you did instead of spending the rest of your life wondering if it was ever in the cards for you.
Like a lot of things that are worth doing, the questions in running are simple. Can I finish the next lap, the next mile, how long can I outlast this cramp, can I beat my last time, those are all very simple, A or B, True or False, yes or no questions. And I think another interesting point that ccunning makes is that at some point, the runner stops making excuses and stops complicating the answer to those questions, they stop saying "oh it's the shoes, it's this fucking concrete," and they just do it.
A lot of people don't understand this feeling, any kind of intense physical exertion to them is just painful and they want to get it over with, but I couldn't live a life in which I never broke a sweat.