Castiel and Sam in “Unfinished Business”

Castiel

Sam, I want Gadreel to pay as much as you do..

Castiel

I mean, I can relate now to how you feel.

Sam

What are you talking about?

Castiel

The only person who has screwed things up more consistently than you...is me. And now I know what that guilt feels like. And I know what it... I know what it means to feel sorry, Sam. I am sorry.

Sam

I know.

Castiel

You know, old me... I would've have just kept going. I would've jammed that needle in deeper until you died because the ends always justified the means. But what I went though... Well, that PB and J taught me that angels can change, so... who knows? Maybe Winchesters can, too.