I have been wanting to devote myself to a martial art for a long time now. I'm lazy and I have a short attention span and I want martial arts to give me some discipline. I've already taken a few classes of both karate and tae kwon do but neither seemed to fit me terribly well. Either my classes were lacking, I was lacking, or some other factor came into play. I'm willing to retry either school. My question is, as a complete newbie to martial arts in general, which one should I pursue? Are particular arts more attuned to certain body structures? I am 6'3" and weight around 170lbs, making me tall and lean (and, according to what I've read, a bad candidate for muay thai). I would just like some advice from veterans and seasoned professionals on the matter. I'm sure it's entirely possible that there is no "right" one to choose, but I felt I should ask regardless. Thank you in advance for your responses.