A little while along the road
Dean's heart was already broken, so when Castiel left him in a puddle of pages and regret, he was numb, incapable of feeling anything but the vast emptiness in his chest.
"Goodbye, Dean." The words echoed around his mind as he tried to come to terms with losing the only thing keeping him here, the only thing he had left that was worth both living and dying for. With trembling hands, Dean scooped up the tear-stained pages, pages that held every moment they had shared together. He'd always hated the Supernatural books but now as he stared at the black and white print he found that he only hated the character whose actions jumped from between the lines. Every fight, every doubt, every tear shed. All the mistakes he'd made written down, unchangeable.
Now
Dean and Castiel sat on the end of the bed, a silent conversation flowing between their tear-laced eyes. Dean swallowed, a hard knot forming in his throat. Without Sam there to be strong for, he didn't know why he was even trying to keep calm. Old habits die hard. His voice was hoarse and thick, his jaw clenched, staring Castiel in the eye. "Cas," he breathed in, his words trickling out slowly and steadily, battling for control over his emotions. "you promised."
"Dean-"
"Just go, Cas. Leave."
He felt a heavy hand on his shoulder, and then nothing. Emptiness. In the silence of the room, he allowed himself to fall apart.
Cas sat alone in a busy diner, the scent of sizzling meat and greasy fries summoning thoughts of Dean, the way he'd smile through a face-full of food, the way his eyes would light up, the way he'd throw his head back and laugh at him and his innocent ignorance. Cas had come here just to remember those times, to remember when there was life in Dean's eyes and happiness in his heart, because he knew from now on the laughter would no longer be twinkling in his eyes, it would be as hollow, as empty, as bitter as his soul was becoming.
He was the Guardian of the Winchesters, and yet Sam was in the depths of Hell and Dean had given up. Castiel had watched over Dean his whole life and not once had he seen him sit back and let the demons win.
"That's crap," he'd replied when Tessa had said that his fate was set, "you always have a choice. You can either roll over and die or you can keep fighting, no matter what."
But he wasn't fighting anymore. By now, Dean had given up trying. Why fight this supposed 'destiny'? The destiny in which the Winchesters were condemned to suffer? Why try to fix something when it would inevitably result in losing more than he could gain, when everything around him would crumble for the sake of holding one thing together? Why try when it was so hard, and hurt so much? The Dean Cas knew would have summoned every demon in the book to bargain with, he'd sacrifice, he'd threaten, he would do something, anything, everything for his brother because without him, he was empty, because he gave him purpose, because he was the only thing he had left. Yet he just sat there staring vacantly at the walls. But Castiel knew what he had to do, something he'd promised Dean he'd never do again. What choice did he have left?