Sam keeps his hand steady on Castiel's hair, feeling the tension and letting it sit there for a moment. Because Castiel has earned it, is allowed to be tense without Sam immediately trying to soothe it away.

He finally settles his hand at the back of Castiel's neck, above where the reddened skin from the night before lay. "I knew there was more going on last night than you were letting me see, but I didn't make the connection with the time of year. And I didn't ask, didn't try to get you to explain why you wanted to be punished so badly last night. I know, you might not have been able to properly verbalize it even if I had, but I should have tried." He goes back to stroking Castiel's hair. "I wish you had said something, though. We could have worked something out without you having to resort to such extremes."