As they stood on that cliffside, overlooking the water illuminated in the sunset glow of mid August, Sam put his hand on Dean's shoulder. He felt Dean start to sob quietly. This was the first time Sam had seen Dean cry since they were young, but he wasn't going to mock him for it. He felt the sadness, too. Cas had been his friend for a long time. Relegated to the ranks of a mere human, he laid out his existence one step at a time, just as they did, and he seemed mildly optimistic.
'But then', he reflected, 'I'm surprised any of us lasted this long. Even if we are worse for wear, sixty is a hell of a big milestone, and we all made it. How is that even possible?' He gazed over the lake, where he and Dean had spent the summer when Sam was eight, and every summer they could after they stopped hunting so many years ago. There were a lot of memories affixed to this place.
Dean took that moment to retreat from this scene to go back to the impala, which had been pulled out of the garage just for this occasion, and retrieve what they were here for. Sam watched as he reached into the back seat and pulled out the box containing all that was left of Castiel Winchester. A fine, white powder, with some fragments of bone. He walked to the edge, and used his hands to scatter the ashes of his husband of twenty five years on the ground and into the water. He steps back, watching the love of his life's remains be blown in the wind, and he could swear that the ashes in the deep pool below formed a wing, before dispersing into the sandy bottom.
"Bye, Cas." He croaked, eyes watering again, "I'll see you."
They turned and walked back towards the impala, not noticing, not able to notice, anything but the footsteps they made, the arms wrapped around each other. They were only able to bear living in the moment.