I wanted to do that last chapter from Sam's POV, along with the original chapter. It's not as good, so I am sorry about that.

Sam nearly wrecked the car when Cas had gotten out before he could stop completely. He quickly found a parking spot and then got out to follow to Dean's room. He didn't see Castiel, which meant he was probably already there and maybe even inside. That was good, at least he could make sure Dean was alright before Sam got to him.

He was going to pummel Dean. First, he breaks his trust by tricking him into accepting the angel that later killed Kevin, and now he was going to leave him all alone. Sam had no one else; he knew he wouldn't even have Cas if Dean managed to succeed in ganking himself. And sure, Sam was furious with Dean and may not forgive him for a long while, but this still was no way to treat family after all they've been through together. He stilled loved his brother, even if he had said that they couldn't be that way if they were to work together.

He guesses he may be just as mad at himself as he is at Dean by the time he reaches the door to the motel room. When he reaches for the handle, though, he finds that it is locked. It remains closed even after he knocks. He hears loud pained noises and he panics, thinking something bad may be happening and they can't hear him knocking, so he begins to pound on the door. He only stops when he hears Cas' voice start to rise.

He listens in on their conversation, ready to burst into the room at any moment should he need to. Eventually, though, he just sits on the ground against the door. He is both physically and emotionally exhausted. Hearing Cas tell Dean that he would kill himself if Dean died was so heartbreaking, and any anger Sam had felt just washed away as the exhausted sadness took its place. He just hoped that Dean would stay alive for Cas. He knew he just wasn't going to be enough anymore.

The room went quiet for a while, and then Sam heard the shuffling of feet. After a minute or so he heard Dean ask Cas why he stays by his side, and after Dean asks again he hears Cas say that he loves him. At those words, Sam gave a contented sigh and relaxed against the door. He knew Dean was going to stick around now, because he had his angel and his angel loved him. Dean was going to be happy, and that made Sam smile for his brother.

Because, above all else, Sam realized now that he finally wanted Dean to just be happy.