"A man can do no more than he can."
I totally disagree with this proverb. If I do not have something, it is me who truly feels how much I need it. I do not talk about feelings only, but knowledge and skills as well. As a teacher, I am not always good at teaching all areas of English language. When I recognize my disability or lack, I work hard to improve that and prove to myself that I can do it.
That's why you should look inside yourself from time to time to talk to the self and listen to your inner voice.