I've been doing martial arts since I was 12, and I started with tae kwon do and got my black belt by the age 14 and my junior instructor certification at the age of 16, and I have been teaching off and on since then.
What you'll get from me and not anyone else is that I have studied every aspect of martial arts, from the physical kinesiology of the movements and techniques we do to exercise/weightlifting techniques and regimen composition and nutrition and eating habits and also the most commonly overlooked aspect, the mental and psychological (spiritual) side which is very important for a well-rounded martial artist and especially for anyone who wants to become a black belt.
As for me, I am a third-degree black belt in tae kwon do but also a black belt in judo, hapkido, tae kuk mu sul, and aikido, as well as being well versed in many more style and arts.
I competed in numerous point-sparring tournaments when I was younger and loved it. I also played high school football and college rugby which also effected effects my athletic style.