Jay, I think the mental strength bit (which I agree with totally) has something to do with feeling good about your body. Running makes us aware of exactly what our bodies can do. It also reminds us that those of us who run (however feebly!) are inevitably much fitter than those who don't. Therefore, being mouthed off by a group of yobs, or grabbed by an attacker, is less of a threat, because we can just sail away (well, that's how it feels, anyway!).
