\Well it smells of cheap wine and cigarettes
This place is always such a mess
Sometimes I think I'd like to watch it burn
I'm so alone, and I feel just like somebody else
Man, I ain't changed, but I know I ain't the same
But somewhere here in between the city walls of dyin' dreams
I think her death it must be killin' me\
Nothing is forever. Dean learned that first when he watched Sammy's nursery and their mother go up in flames twenty-two years ago, and again when Sam walked out of their life to chase his dream of normal. He only finds out later that Sammy wants to be a lawyer. He finds it funny, that his little brother wants to bend the truth around his little finger for a living. He figures Sam would be good at it; he certainly is at bending Dean to his every whim when he wants to.
Nothing is forever. Sam knows that as well as Dean does. He taught that to his big brother the night he left for Stanford, though he'll never know it. He learned it himself the night Dean brought him back from Jericho, the night of Jess' death. He thought Stanford was it for him. Jess was the one, he was finally going to have a normal, safe, constant existence.
Then the demon took that away from him, and the longer he's hunting it the more he realizes, somewhere in the back of his mind, that he won't be going back to school. Stanford seems more like an illusion to him the more time he spends back with Dean, a flowery, magnificently whitewashed palace of dreams come true. But the reality is Sam's ballroom clock has struck midnight, his fairy godmother was never there in the first place, and the glass slippers are cutting right to the bone.
So he gradually forgets about the ball, remembers only the beautiful, shining princess, and slowly tries to piece the glass shards of his life back together for the second time. Only this time he's not a stranger in a strange land; this time, he has help from the beginning from someone who loves him, and that makes all the difference.
Forever is boring, his brother once told him.
He thinks, maybe, that Dean's right.