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

Sam Winchester: Lesson? What lesson?

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