I didn't proof-read or rewrite this or anything. I just wrote it because I needed to, because I needed to give these thoughts the attention they didn't get in the episode. Feel free to ignore me, cause this is poop. SPOILERS FOR 7x02.
Dean doesn't know what to do.
He's sprawled on the ground, burnt rubble of Bobby's house behind him, and for the first time in what feels like forever, he's dangerously close to losing his shit and bawling into the gravel. He's never felt this thoroughly destroyed before, not even in hell when there was nothing left of him but bones and a tattered soul.
He's lost damn near everything.
He can't bring himself to dwell on Cas, can't let himself stop long enough to think about his best friend the angel, and the trench coat that likely burned up with everything else. Can't think about how he never properly said goodbye, never got to tell him how much he meant, how close to family he really was, anything. He won't let himself, because it would mean wallowing in the loss, unable to pick himself up and fix all the other shit coming down around him.
He will not allow himselt to think about the house, either; the eclectic interior, the mass of books lying around, the thick layers of dust on things that haven't been touched since Bobby started hunting. He won't let himself think about everything that they lost, all the research and weapons and Bobby's panic room. The memories threaten to pull him down, the implications that this was the closest thing they had to a home and it's been burnt to the ground. He won't linger on the irony of the situation any longer than he has to.
He absolutely won't concentrate on the fact that everything is completely out of his control, that Bobby is missing and his leg is broken and the Leviathan are the most terrifying evil he's encountered so far. He can't think about how nothing ever goes right, how he seems to be the prime example of Murphy's law in play, how the world is almost always crashing down around his feet and there's never a break in all the shit that's dumped on them.
He will not dwell on it, because it will break him down.
Instead, he focuses on Sam, on how he's laying there on the ground, unresponsive as death. Dean scoots as close as he can, threatens to call the paramedics and desperately shakes his baby brothers shoulders, trying to wake him up. He needs Sam to be okay, needs it so much that he doesn't know how he'll cope if he's not.
Because, with everything that's happened - Cas gone, Bobby missing, the Leviathan, and charred wood and ash where a house once stood - Sam is all Dean has left.