a) be humble. as socrates said, the first step in wisdom is admitting you know nothing.
b) try to absorb all the knowledge you can. don't argue, but don't be afraid to ask for clarification.
c) take criticism as something you can better yourself with, not something to feel bad about. work hard, set your goals reasonably, and make sure you are able to train as hard as you need to to meet them. and then stick to that training. reset your goals if you need to, no one is perfect and no one can predict the future.
d) try not to complain. that doesn't mean you should be reluctant to speak up if you are injured or not quite ready to go another session, but don't whine. that's the quickest path to earn the derision of your peers and instructors. your best effort will be more appreciated than simply sitting out.
most any gym /dojo that's worth being at will respect someone who exhibits these qualities, regardless of their skill or ability upon joining.
His helmet was stifling, it narrowed his vision. And he must see far. His shield was heavy. It threw him off balance. And his target is far away.