I serve Heaven, I don't serve Man. And I certainly don't serve you.
The words echo in Dean's head, over and over, more forceful with each go around. And he can't stop it from hurting, can't make the syllables mean something less. Because you can't take something like that back. As much as he wants Cas to just swoop in an apologize to him. Dean knows he won't. Knows he can't.
And that's what hurts the most, he guesses.
Because he sort of understands, maybe. He gets what's going on and he doesn't like it. Not one bit.
He'd blown Cas off when he'd admitted to getting too close to the humans in his charge. To him. Dean had wanted to laugh then because he didn't think it was possible. An Angel letting its guard down for the likes of him, a man too lost to be found. It'd sounded like something Stephanie Meyer would write, not the kind of thing that actually happened in real life.
So he'd let it go. Dean put it to the back of his mind, locked it away so that one day he could remember it for what is was worth. And that maybe it would mean something more than Cas had set it up to be. Because if Dean was really being honest here, he really did want everything Cas said to hide some deeper meaning. He's never really been a black and white kind of guy, except when it came to Sam. 'Cause either you're drinking demon blood or your not, there is no middle ground there.
Dean fists the collar of his jacket to his face, trying desperately to block out the image of his little brother's mouth covered in blood, demon blood. Not Ruby's this time, which he's sort of glad for. But the fact that he still stood there and watched Sammy suck on some demon bitch's neck like he was in some kind of cheesy vampire movie. He shudders, entire body quaking at the image permanently seared in his brain.
Dean doesn't want it there. He doesn't want to remember Sammy that way. But he can't make it leave. Just like he can't make Cas' words stop hurting. Just like he can't stop everyone from fucking leaving him. Alone.
Always so goddamned alone.
And, maybe, he gets that too. Because he's supposed to be the righteous one to finish this, or however Cas put it back then. And righteous men are supposed to be lonely bastards, he guesses. Which he's used to being, you know. He and Sammy had to fend for themselves for years. What's a couple more if it means the world can keep spinning on its happy little axis? It's not like the world ever cared much for him anyways.
Dean's just a ghost among six billion, very much alive, souls.
Cas made that very clear the moment he said he'd learned his lesson in Heaven. Dean can read between the lines. He can see the other side of this and how it will likely end. He's just so tired of always being the one grasping for straws. Just once he'd like to be the one to say, "Fuck it!"
And actually mean it.