In 7x02 we see Sam dig into a fresh cut on his left hand in order to ground himself in the face of his Hell hallucinations. Since then (and long after the wound has healed) Sam’s used the same technique in other moments when he feels uncertain about reality.
Supernatural Meme - [3/7] Relationships Hey, Castiel. Um… Maybe this is pointless. Look… I don’t know if any part of you even cares, but, um, I still think you’re one of us, deep down. I mean, way, way, way off the reservation, but… Look, we still have till dawn to stop this. Let us help. Please.