Taika Waititi explains that the entire training sequence in The Empire Strikes Back is something he didn’t appreciate when he first saw it.
There’s a depth to all of it, and Yoda’s statement, that a lack of belief is cause for failure, that you don’t necessarily see when you’re a kid watching a Star Wars movie for the first time.
But then, later when you watch the scene again you see how Yoda’s line actually says a great deal.
Empire Strikes Back Yoda training Luke part 3 "Try not. Do. Or do not. There is no try." (HD)