Trickster and Sam in “Unfinished Business”

Sam, there's a lesson here that I've been trying to drill into that freakish Cro-Magnon skull of yours.

Sam

Lesson, what lesson?

This obsession to save Dean. The way you two keep sacrificing yourselves for each other. Nothing good comes out of us, just blood and pain. Dean's your weakness. The bad guys know it, too. It's gonna be the death of you, Sam. Sometimes, you just gotta let people go.