A sport that most consider to be fun to do or to watch, and that the three people before me are making look like a boring sport with their lengthy explanations. The only main objective is to get from point A to point B as quickly as possible in your environment, but there's a reason it's a "sport" and not an "obligation". Have fun in your sport- take a little time to perfect a jump over something if you constantly see that you're messing up on it, let yourself get sidetracked and go chase a squirrel, go out of your way to climb up on top of McDonalds and dance around on the roof to make a fool out of yourself and then run like a madman when the workers are chasing after you shouting that they've called the "poh-leece on you!!!" Have fun, do what you can, and learn what you can't. Climb up on a Church and watch cars go by, push your body to it's limits. That's the perfect world of Parkour... not just discipline, but enjoying disciplining yourself.
Parkour rocks my socks... and the socks prevent blisters. Lol.