The worst thing about falling isn't the pain. Although that's got to be on the list- a single trip leaves his palms and knees stinging and red blood welling up above the skin. This new-found human frailty leaves him constantly paranoid, not wanting to move in case he injures himself, all too aware of the brittle bones beneath his paper-thin skin, wondering how humans even manage to get up in the morning knowing how delicate and fragile they are.
It isn't the new sensations, the biting chill of a sudden breeze that has him zipping up his jacket, or the way his stomach twists and growls when he realises he hasn't eaten for almost a day, or that irritating itch in the one place he just can't reach.
It's not the way his body betrays him, eyes stinging and throat swelling until he can barely speak whenever he thinks about what happened, what he has done. He can't control the way his hands shake when he is afraid, or the way blood creeps into his cheeks and flushes them a deep scarlet when he is angry. For a being who has lived so long in total control of his vessel, having a body that communicates by itself and gives away his emotions when he tries to keep them hidden bemuses and terrifies him.
It's not the sense of helplessness that follows the loss of his powers. Every time he forgets for a second and tries to disappear, or to heal, he is overcome with a crushing sense of uselessness, weakness. He is reminded once again of how powerless he is now, and questions why he even tries any more, why he bothers to go through each day now he has lost the only thing he was ever good for.
It's none of these things.
The worse thing about falling is the loneliness. He never realised how utterly isolated human beings are. For millennia, even when apart from his brothers and sisters he could still hear the low hum in his head that was their chatter, a constant stream of information he could tune into whenever he liked. If he chose to ignore it, it was always there, a background noise, a safety net, telling him he was never by himself.
Even after he had been cast out, abandoned from Heaven, he was never alone. He was always connected to the brothers, could always sense their whereabouts, their emotions, their thoughts. The symbols carved onto their ribs were supposed to help him keep track of them, but they did so much more. They helped him to keep them safe from danger, to check up on them, to let him know that whatever happened, they were okay. Now he has no way of knowing if they're even alive.
But even worse than that, he doesn't get to hear their prayers any more. The familiar voices in his head that kept him going, through civil war and madness and Purgatory itself, his reason for living, that small whisper that reminded him what he was fighting for, that he was needed, that he was wanted, that family doesn't end with blood- gone. All he has left is his own voice, reminding him of his failures. And now, for the very first time, he understands what it is like to be human, what they go through every single day, what greets them as they wake up the morning and what keeps them awake into the early hours of the night.
And it terrifies him.