Summary: Sam is trying to be strong, but falls apart after seeing the bruises on Dean's neck.
Sam's proud of his ability to not fall apart after everything that happened. He needs to be strong. For Dean. He's done a lot of bad things, and Sam knows that.
Two days after setting Lucifer free, Dean and Sam are eating a pizza in their hotel room, celebrating the fact that Dean killed Lucifer and the Apocalypse has been averted.
Dean's grabbed his second slice and Sam is already done, when he notices the bruises on Dean's throat. That's when it hits Sam that he nearly killed his brother.
"Oh God," Sam chokes out. He gets up fast and bolts towards the bathroom. He locks the door and begins to sob.
"Sammy, what's wrong?" Dean asks his younger brother. Sam just fell apart out of the blue and Dean doesn't understand why. He had been expecting a Sammy breakdown, but not this soon.
"Leave me alone," Sam sobs. How can he ever face his brother again? How can Dean ever forgive him?
"I can't do that, Kiddo. Now tell me what's wrong." Dean's really worried and about to kick down the door.
"I nearly killed you," Sam tells him after a few minutes. He can't believe he did that.
"Oh, Sammy," Dean says and then kicks down the door. He should have known that would kick-start Sam's breakdown.
"I'm so sorry, Dean. I wasn't thinking straight and then you called me a monster and I just lost it and I can't believe I did that," Sam rambles. He can't stop talking.
"Sammy, it's partially my fault. I forgive you, Kiddo." Dean knows that forgiveness is important to Sam.
Sam hugs Dean and stays in his brother's arms for arm. He's a teensy bit clingy sometimes.
Everything is okay again.