The first thing you must realize: movement is personal, make it into what YOU want. Your life is what you make of it, whatever you want to train, go for it. If you want to really specialize in one form of movement, that's great go for it. Honestly, learn as many or as few of the disciplines that you want: your body, your choice. However, whatever you do, do it well. Practice a lot and understand the reasons for each discipline. If you can grow physically and mentally from whatever discipline(s) you practice, that is when you know you are doing something right. Just be safe, have fun, learn and move your body! Personally, I love parkour for what it means to me mentally and the prowess it gives me physically and I will always respect it. That's not to say that I want to limit myself to it, I want to learn martial arts, dancing, and a possibly dabble in free running. Just learn, progress and stay fit, these are the important things to remember; arguing on forums is fruitless, find your own definitions, just know what your discipline originally meant to teach.