Motivation = Reason Times Plan Minus Pain

If motivation equals reason times plan minus pain, and we're focusing here on the reason, this is the big reason why you want to do the thing. In high school, I ran cross country and tracked my freshman and sophomore years. Running was painful. It's not super fun in and of itself. And I wasn't very fast. My motivation was incredibly low. Even ever since then, I've never really enjoyed running. But one of my friends recently in the past few years got into ultra running. He now says he actually enjoys it. So what gives what? How is it that one person could be so motivated to do something extremely painful while another person had less than zero motivation to