Well, here is the final part, set in 2009, Dean's POV. Not sure I'm very happy with it, but here you go.

"Don't ever change", is all Dean can think of saying to Castiel when he returns. Then again, his most pressing concern at that moment is to get hold of Sam, fix that part as fast as he possibly can. He can deal with the angel later.

When later comes, and they've bought some hamburgers and beer at a roadside diner, and then drove a little further until they found an abandoned rest-stop, Dean wonders what to say. Castiel is eyeing the hamburger almost suspiciously, and Dean knows he doesn't need food, but convinced him to try anyway, because they're supposed to be the best in the state!

What Cas, future-Cas, told him in the car keeps running through is his head, like a broken record.

Tell him to leave. Tell him to go back to Bible camp, tell him to become that good little soldier again.

And then,

I'd be better off if I'd never met you.

Dean looks at the angel in front of him, who's apparently decided he does like hamburgers, wonders how he could ever transform into… that man, the broken, hopeless drug addict from 2014.

"Don't ever change", he says again, and Castiel swallows the last mouthful of his hamburger.

"What do you mean by that, Dean?" And the words come pouring out; he tells Castiel everything that happened in the future, everything about his future self, everything about the future Cas. Castiel listens with his head slightly tilted, and Dean is desperate to make the angel understand why he can never, ever change.

"Please never become… like that, Cas, please. Promise me you won't." Blue eyes meet green, and Dean once again feel a flood of relief when the angel's eyes are clear, not clouded by a haze of drugs, nor dead and cold and hopeless.

"I promise, Dean."

"You know what he told me, Cas? He – he told me he'd been better off if we'd never met. And that I should tell you to, uh, go back to Bible camp, and become that good little soldier again."

"Why?"

"Because… it wasn't worth it." Dean takes a sip of his beer. "I won't let that happen to you", he vows to the angel. "I won't let you become that. I'm not gonna let Sammy go dark side, and I'm not going to let myself end up like that cold dick, and I'm not letting you change." He holds Castiel's gaze, and a small smile appears on the angel's mouth. A smile that is so Castiel, and nothing at all like the bitter, drugged, too wide smile of Cas, that Dean can't help smiling back, despite everything.

I'll be damned, but the end wasn't all angst. I hope you like it anyway!

You are very welcome to drop one final review!