Happiness would come, Harry thought, but at the moment it was muffled by exhaustion, and the pain of losing Fred and Lupin and Tonks pierced him like a physical wound every few steps. Most of all he felt the most stupendous relief, and a longing to sleep…he turned away from the painted portraits, thinking now only of the four-poster bed lying waiting for him in Gryffindor Tower, and wondering whether Kreacher might bring him a sandwich there, "I've had enough trouble for a lifetime." (1)
Leaving Dumbledore's office, Harry, Ron and Hermione set off toward Gryffindor tower, walking slowly, feet shuffling, often having to redirect themselves down a back passage to avoid debris or broken staircases. Eventually, they reached the common room, where they found a crowd of people, mostly asleep though some were lying with their eyes open, lost in thought, occupying just about every surface possible, and Harry wondered if they would find the dormitory full as well. He thought wistfully of his four-poster before climbing the stairs to find out for himself whether or not the bed was indeed empty, Ron saying a quick goodnight to Hermione before following him up the spiral staircase. He was pleased to find that someone seemed to have the sense to leave their beds open, though the other three were all occupied. Harry didn't even bother shedding his grimy clothes as he fell onto the bed, wriggling to get the blanket pulled over him, and almost immediately dozing off. He vaguely registered hearing footsteps a few moments later and Hermione's voice talking to Ron, asking if she could sleep in here because all the beds in her dormitory were taken, before his brain completely gave in and he fell fast asleep.
Harry woke to darkness and an empty dormitory, feeling rested, but still tired, like he would need to sleep again in half an hour. He surveyed the room, taking in the damage for the first time – there was dust everywhere, one of the windows blasted out by a curse, leaving a hole slightly larger than the original gap, and the occasional piece of stone was scattered across the floor, but on the whole, the dormitory looked no worse for wear.
There are things that need to be attended to, things Harry must do, people he must talk to, but right now, his muscles sore and his body fatigued, 8 months of dirt and grime built up from their stint in hiding (even if he did use a cleansing charm, its not the same), all Harry can think of is taking a hot bath. So he makes his way into the adjacent bathroom, turning the faucet on and checking the temperature with his toes before sinking into the water, groaning with satisfaction. Even after only seconds, he feels like he is being healed, the water soothing all the parts of him that hurt. All the physical parts, at least.
The only thing it isn't helping is his mind, which is still buzzing with a thousand different thoughts. He's relieved, beyond relieved, that it's all over, Voldemort is gone, the battle is won. The great weight that's been hanging over his shoulders his entire life is lifted, and he doesn't have to keep looking over his shoulder every second the way he has for the last few months (though admittedly, it'll probably take a few months to break that habit). But he hates himself for feeling this way. He's just lost friends – Fred, Lupin, Tonks, Lavender, Colin Creevey, who knows how many others? – he should feel sad. And he does, but mostly he feels relief. Shouldn't he feel sadness first? Why doesn't he? Is there something wrong with him? He can't bring himself to face the Weasleys until he knows why he doesn't feel worse. He feels responsible, he is responsible, but still, relief flows over him. He wants someone to talk to, and yet, at the same time he doesn't want anyone to know this about him. Let them think I'm grieving just as much as they are, he tells himself. Maybe if I pretend long enough, it'll happen.
He's shaken out of his reverie when the door to the bathroom slams open, revealing Ginny, looking anywhere but at Harry. At first he thinks she's trying to respect his privacy, but since when had Ginny been shy about that? When he sees her fold her arms across her chest and notes the clench of her jaw, the hardness in her eyes, he knows she's angry, furious even, and he feels his stomach twist.
"Mum wants to know where you are," Ginny says, still not looking at him. "She's worried about you. She's been through enough."
She flashes him a quick look that tells him to get his ass down to the Great Hall before she kicks it. He nods, and she turns to leave, slamming the door again behind her. Harry sinks low in the water, blowing bubbles out through his nose as he lets all the air in his lungs out, and he rakes a hand over his face and through his hair. Shit.
(1) Harry Potter and the Deathly Hallows, pp 598, 600