I feel the need to jump in here and say that it's a myth that adult brains learn more slowlly than teenage brains. That's been disproven many times over by now.

Don't let all this stuff keep you from your aspirations. Everyone who ever did anything worthwhile did it in the face of a whole bunch of people telling them why it couldn't be done.

So I renew my advice: don't ask for permission. Just practice, get amazing, and prove the naysayers wrong.