Star Wars Episode V: The Empire Strikes Back1980

[Luke sees his X-Wing is about to sink into the bog]

Luke Skywalker:
Oh, no! We'll never get it out now!

Yoda:
So certain, are you? Always with you, it cannot be done. Hear you nothing that I say?

Luke:
Master, moving stones around is one thing, but this is... totally different!

Yoda:
No! No different! Only different in your mind. You must unlearn what you have learned.

Luke:
All right, I'll give it a try.

Yoda:
No! Try not. Do... or do not. There is no try.

[Luke tries to use the Force to levitate his X-Wing out of the bog, but fails in his attempt.]

Luke:
I can't. It's too big.

Yoda:
Size matters not. Look at me. Judge me by my size, do you? Hmm? Hmm. And well you should not. For my ally is the Force, and a powerful ally it is. Life creates it, makes it grow. Its energy surrounds us and binds us. Luminous beings are we, not this crude matter. You must feel the Force around you; here, between you, me, the tree, the rock, everywhere, yes. Even between the land and the ship.

Luke:
You want the impossible. [sees Yoda use the Force to levitate the X-Wing out of the bog and gets flustered when he does it] I don't... I don't believe it!

Yoda:
That is why you fail.