If the trainer gives up on you, that is his failure as a master, not your failure as a student!

You're training to learn something, after all. If you knew everything already, there would be no need to train.

As long as you haven't started getting muscle dystopia from old age, it isn't too late to start. Just don't expect to enter a world championship anytime soon.

Personally, I am practicing kyokushinkai karate.