Dean and Sam in “Unfinished Business”

Dean

Sam. [holds Ruby's knife out to Sam] If you're serious, and you want back in... you should hang onto this. I'm sure you're rusty. Look, man, I'm sorry. I don't know, uh, whatever I need to be, but I was, uh... wrong.

Sam

What made you change your mind?

Dean

Long story. The point is... maybe we are each other's Achilles' heel. Maybe they'll find a way to use us against each other, I don't know. I just know, we're all we've got. More than that... we keep each other human.

Sam

Thank you. Really, thank you. I won't let you down.

Dean

Oh, I know it. I mean, you are the second-best hunter on the planet.

Sam

So what do we do now?

Dean

We make our own future.

Sam

Guess we have no choice.