What kind of master do you have to learn from? You should learn Taekwondo
from a master who knows the principle, who knows the way. Not from a
strong master. As far as it is you, a weak man, who want to be stronger.
The training of Taekwondo is like a journey what goes ahead for a distant
place. If you are not observing another's journey but you want to make
your own journey, what you need is not a fellow of strong legs but a
helper who knows exact ways. Although he or she may not even walk, since
he or she has no leg, they should be able to draw exact map.
They are all the same in Taekwondo, too. If you want to be protected
you should follow a good fighter. But if you want to be stronger yourself
you should follow those who know the best way, the method to be stronger.
Even when they might be an old man or a weak woman, or even when they
might be some books that give you mere explanations.