Sam understands. He looks at Gabriel, with his wild, vacant stares, and he understands. He's been there.
After Hell, and Cas, and the Wall, he shut down. It was easier - is easier - to just drift away from himself, pretend that the world didn't exist, and neither did he. It's quiet, inside his head. He can just float, and forget about the world that's probably about to end again. He can forget about everything, for a time.
It freaked Dean out the first time it happened. That is, the first time it happened when Dean was around. Sam's sure it happened before.
Dean hated it, the way Sam just flipped the switches, turned the lights off in his brain. He didn't seem to get that this was better than dealing with the memories of... well, of everything. Fire and brimstone, and all that.
Dean hated it, because Dean's always liked to feel. He'd never admit it to anyone, but Sam knows his brother too well to be fooled by the macho, devil-may-care façade he parades around with like a shield. Dean wears his emotions on his sleeve; Sam prefers to keep his locked up, tucked away in a corner of his mind labelled 'DO NOT OPEN'.
'Course, there was a time when it wasn't always like this. Sam remembers that time, vaguely. Things were so much simpler back then, his thoughts and memories not quite so jumbled. What can he say, the millennia of torture fucked him up a little. More than that, though, it was the coming back that really knocked it all out of whack. He can't quite reconcile the Sam that jumped into the Cage with the Sam that came out of it, because the Sam before didn't have a soul that was far older than the body it inhabited. It didn't have all those memories from two separate lives, somehow lived out simultaneously. But the Sam after? He had too many memories to fit into one mind. So, when they began to leak, it was only natural to want to get away. It was the only way he managed to stay sane for as long as he did.
Trouble was, Dean expected him to be the same as before. He expected Sam to be the little brother who hadn't been through Hell and back, who hadn't spent a year (a thousand of them) without a soul, who didn't understand the true horror and beauty of an archangel's face. So Sam tried, as hard as he could. He dug himself out of his mind, time and time again, because he had to. Because Dean needed him to.
Sam looks at Gabriel, and he sees himself. He doesn't know if Gabriel knows what's going on, or where he is, or who Sam is, but he has to believe that Gabriel is not lost, as Cas said. He can't be. The world needs him.
A/N: So... Short and sweet? Short and terrible? Nonsensical? I don't know. Please leave a review and tell me, if you have a moment.