He didn't really know what to do after the war.
First there was a scuffle. Voldemort's body hit the ground, and everything seemed to stand still. Death Eaters disapparated, some tried to reach his body, only to be torn apart by the crowd that surrounded Harry. Whoever was left, disappeared.
Then there were the trips to St Mungo's, countless people flooding in battered, bruised, cursed, crushed. Children ferried off by side-along apparition until the waiting room filled up and St Mungo's came to them. Everyone huddled in the Great Hall, dirty and worse for wear, the dead lined up on the floor.
After that came the funerals. This probably hurt the most. Remus and Tonks laid side by side with a doubly wide tombstone to share. Colin Creevy in a tiny coffin despite only being a year younger. Snape, who was awarded with an Order of Merlin. He didn't know how to feel at that one.
And then, there came the cleanup, teams of wizards were brought in to put Hogwarts back together, instructed by the teachers. This was also when the press decided would be prime time to hound anyone involved for interviews, and he was of course the most highly sought out of them all. This was the part he hated most. He agreed to do one for Luna, so that people could hear it from him instead of a twisted one from onlookers. He only spoke about what everyone else knew, break into Hogwarts, start a fight, kill the Dark Lord. He turned down every other offer.
And now, it was over. He'd done his duty, attended the minimum required amount of events and gatherings. He wasn't needed in the Hogwarts repair team. No one could got back until they had functioning dorms and classrooms again so school is postponed until further notice.
When his body hit the ground, all he could feel was relief. Overwhelming relief, that this was finally over. All he wanted to do was sit down, after days of being on his feet nonstop.
Now, lying on a bed in Grimmauld Place, staring at the ceiling, not bothering to light a lamp or open the curtains, it felt wrong. His whole body felt numb, like it wasn't entirely in the physical world. He barely felt the floor where his feet met it, dangling off the edge, not even having the energy to lie down properly. With the one thing that's been hanging over his head since he was eleven, the thing he was told by everyone was his duty, if not destiny to do, well, done, he felt wrong. Empty. His life's purpose had been realised, what was next? Give Prophet interviews for the rest of his life?
He felt disgusting, thinking this way. Voldemort is gone. He killed countless people, ruined lives of countless more, ruined his from his very first birthday. Everything in his life has been a direct result of that.
And here he was, annoyed and empty that he's dead.
He hasn't touched his broom. Every time he thinks about playing Quidditch, or just flying, a nagging voice reminds him it's not safe. You'll be seen. He can't shake it, this feeling of alertness. Not even when he's lying on his bed in this vegetative state, the voice yelling You've got to move! They'll find you! But he won't, or maybe he can't, lift himself up. so his heart just races as he lies still, reprimanding himself. Get up! Why won't you get up! You need to move!
He must've been there for hours, he thinks.