How do I get off the couch?

I do wear one of those fancy FitBits, though, which means I at least have some sort of aspiration to exercise. I go to the park across the street a couple times a week to "get my steps in". There I see young people and old people and couples and dogs and even kids jogging along looking all glowy with the sweat of a fit person, and I think to myself, "It must be nice to be so strong and awesome like that." I get uber jealous of runners sometimes.