“No man knows what he can do until he tries.”

“The power which resides in him is new in nature, and none but he knows what that is which he can do, nor does he know until he has tried.”

“A man doesn't know what he knows until he knows what he doesn't know.”

“Knowing yourself means knowing, first, what it is to be a person; secondly, knowing what it is to be the kind of person you are; and thirdly, knowing what it is to be the person you are and nobody else is. Knowing yourself means knowing what you can do; and since nobody knows what they can do until they try, The only clue to what man can do is what man has done. The value of history, then, is that it teaches us what man has done and thus what man is.”

“It only shows how true the old saying is, that a man never knows what he can do till he tries, gentlemen. From "Pickwick Papers" ch. 49 page 646”

“You don’t know what you can do. You won’t know until you try.”