I just got done doing something I haven't done in a long time. I ran 1.5 miles [Edit: 1.73 miles on the Garmin, I just learned]. I've always hated running. I'm not all that athletic to begin with. I'm tall and thin, but my legs are kind of short for my height. Not freakishly short, but short enough that my height doesn't really give me an advantage for speed. My lung capacity isn't all that great either, despite relatively good health, I have a hard time breathing while running, or swimming, or any other high intensity activity. So last night when a coworker asked me if I wanted to go running with him today I surprised myself when I agreed to go.
Why did I agree? Because I've been itching to go for the last year, I just didn't realize it. A year and a half ago I started eating Paleo, and it seems every day I have increased vitality, and my body wants to do more and more. I've slowly built up more and more free weights. I put in a make-shift pull up bar in the garage. When I take my son to school and pick him up, we run most of the way. We chase each other in the park. The list goes on. I've more or less unconsciously increased my activity by orders of magnitude since I've started eating better. I've never said "I'm going to go out and run", it just happens when I'm already out. Naturally, it's a positive feedback cycle. Better diet => more vitality => I have more energy to go out and do more => I get the exercise I need => more vitality.