"It's like being strapped to a comet."
When all of heaven came crashing down, Castiel was forced to watch as his brothers and sisters went with it. Their wings and memories were forcibly ripped from them, to leave them freefalling without any resemblance of their former grace.
In a sense, his own were not torn away, but rather were clipped carefully because Metatron wanted him to remember. He wanted Castiel to know that those were not falling stars that lit up the sky.
It could be said that he wanted him to suffer even with a happy, human life. He wanted him to be forever reminded of the fact that he used to be so great.
Metatron wanted it to show how far he'd fallen.
Despite the precision of what he'd done, it had still been very painful to feel his own wings—or rather, what was left of them—once so magnificent, now crushed and battered. In the end, he'd had to remove them himself.
It hadn't been nearly as clean a cut as what had originally destroyed them, leaving him with hours of agony as he lay out in the tall grass, alone. Tears streamed down the fallen angel's face as he watched the sky, on his back after it was over.
The sight of his family falling to earth was both beautiful beyond belief and equally terrifying.
Even after his own cries died away, he was left with the sound of the angels whooshing through the air, falling in flames. That unbearable noise, too, eventually went away. The sky was alight no more.
It was over.
Time passed slowly and monotonously.
He heard no angel chatter, because there were none left that remembered. No news came of whatever fate had befallen to the Winchesters. Castiel could only hope that they were alright, for both their sake and his.
He spent the majority of his time at restaurants, motels, and the like.
Over the course of his first year as a human, he made a point of understanding every reference that Dean had ever made to him.
There was nothing for months.
It was November when he heard Dean's voice again; an early morning in the middle of the month when even the laziest of residents put away their Halloween decorations.
He was awoken rather abruptly to hear the closest thing he'd ever had to a best friend speaking, sounding panicked and in pain. Of course, he was awake and alert very quickly. Castiel couldn't hear the hunter very well, but he could make out enough to get very worried very quickly.
"Cas…um…I don't—oh god, Sammy—I don't know if you can even hear me but we need you, man. Hold on, you'll be okay, Sam. Look…it's bad, Cas. If you can get over here, please just—just do it."
After that, there are only very loud growls and noises that can't possibly be human by any stretch of the imagination.
"Dean…"
The fallen angel's eyes are wide and panicked as he goes stock still, face contorted in desperate concentration. He tries over and over again to fly to them. In this moment, there is absolutely nothing more on this earth that Castiel wants than to be human.
It takes six hours before he finally gives up.
He lies on the floor, a curled up, sobbing mess after he realizes his failure. He couldn't save Sam and Dean. As a human, he was absolutely useless.
Castiel does not move for another whole day. He just lies there pathetically, cursing Metatron's name and screaming himself hoarse.
All of heaven fell, and so did he with it.