Disclaimer: I'm not JK Rowling. If you didn't guess that already ...
Harry didn't quite realise it, but he was roaming the corridors absent-mindedly, all his thoughts focused on what had happened the previous night. Because of him, Sirius was dead. If Harry had thought about it, found a better way to check that Sirius was there ... who knows what might have happened? He wouldn't have gone, and Sirius could tell Dumbledore, and Dumbledore could capture Lestrange and the other Death Eaters who had attacked Harry and his friends. If he'd thought to fly the Thestrals to Grimmauld Place instead of straight to the Visitors' Entrance of the Ministry, Sirius would be alive. If he'd opened the Christmas present his godfather had given him, a paired mirror that allowed him to contact the owner of the other mirror, Sirius would be alive. If he'd been prepared to fight an ambush, which he should have been if he thought he knew that Voldemort was there, Sirius would be alive.
Stopping suddenly, Harry felt his anger and rage growing inside him, and swung a fist at the wall. It hurt, but the pain made Harry feel more alive, in a twisted way. It also made him feel guilty, knowing that Sirius would never feel pain, or pleasure, or love, or jealousy, ever again, because Harry Potter was too much of a bloody Gryffindor to think out his actions beyond "run in madly and save Sirius from the Big Bad". He spat out a word that would have him being scolded by anyone who heard it, before punching the wall again. He heard the crack of bone in his hand, but didn't care. If he damaged himself enough, Voldemort would consider him an easy target, and he'd get to see Sirius again. A thought flew into his head, and he began to run towards the Astronomy Tower.
"Harry?" Angelina Johnson called out her Seeker's name cautiously, as she stepped into the fifth-year boys' dorms. Ron Weasley and Neville Longbottom had approached her, asking her to go up and check on him. They were sure that he was up there, but when they'd tried to go to check on him, they'd been met with a spray of various jets of spellfire. So, being good friends, they turned to one who'd been a good influence on his life and served as a role model to him. Angelina would have offered anyway, understanding what Harry was going through. Sirius Black, Harry's godfather and only real parental figure, had been killed in the Ministry of Magic the previous day, and he had survivor's guilt because of it.
"Harry?" She called his name again as she walked into the centre of the room, heading towards his bunk. She couldn't see him anywhere, and figured it was likely that he'd snuck out without Neville or Ron noticing. Blokes tended to be less observant anyway, in her experience.
Stopping by his bed, she noticed that there was a familiar-looking scrap of parchment on his dresser. Picking it up, Angelina muttered, "I solemnly swear I am up to no good." She'd learned the password two years ago, after having snuck out with the twins, Lee, Alicia and Katie to play strip poker in one of the unused classrooms. One of the twins had always had one eye on the Marauders' Map, to make sure they weren't caught, and Fred had explained what the Map did to her. Obviously, Fred and George had given Harry the Map at some point, before their flamboyant jailbreak earlier in the year.
Scanning the Map for Harry's name, she spotted him running towards the Astronomy Tower. That wasn't a good sign. In her experience, when you ran to the top of a tall tower after a sudden bereavement, you weren't going to admire the stars.
Harry sat on one of the parapets, looking down at the school below him. From this height, it looked like a toy to him, with barely-noticeable specks that were various witches and wizards running around. If he'd brought the Map with him, he could find out who they were, but he hadn't. He wanted to avoid all people, but he wasn't going to be sneaking around under his Cloak with the Map in order to avoid them. In addition, it hurt too much to look at the Map, or any of his legacies from Sirius or his dad.
He wondered what his body would look like when they found it, and if he would go on to the afterlife as broken as he left the current life. He'd be with Sirius and his parents though, and that was what mattered to him. As he stood, and raised a foot to step over the edge, a pair of hands grabbed him and pulled him to safety.
"What the hell are you thinking, Harry James Potter?" Angelina slapped him across the face, hard. "You may be a good flyer, but you can't bloody fly without a broom!"
Harry slumped to the floor, and tears began to roll down his cheeks. "I was ..."
"You were going to kill yourself, you idiot!" Angelina couldn't help but shout at him, trying to get him to see how foolish he was being. "Do you think Sirius would want you to do that?"
Those simple words got through to Harry much more than the slap did, and Angelina realised how badly he was suffering. She sat down beside the young Seeker and pulled him into a hug, which he returned desperately, still crying.
"Harry." Angelina's voice was softer now, almost soothing, as she stroked the boy's hair while holding him close. "I didn't mean to upset you, but you should listen to me." She kissed his forehead, before continuing. "The twins told me all about what's happened with Sirius, about how he's innocent and never got a trial. Believe me, we all wished you'd be able to go and live with him, particularly when I heard from Fred about how your aunt and uncle treat you. But the best thing you can do now is honour his wishes. He must have wanted you to live well, not throw your life away because of his death."
"Angelina ... It's my fault." Harry's voice was little more than a whisper, but she heard it clearly, and held him closer. "I killed him."
Angelina took hold of his chin and lifted it, looking him right in the eye. "Did you cast the spell that killed him, Harry?" He shook his head slightly. "So don't blame yourself for it. He went to the Ministry to save you, didn't he?" He nodded. "He died to save the thing he saw as most precious in the world to him: you. The son of his best friends. Repay the favour he did you, and live, Harry." She got a sudden instinct, and kissed him on the mouth. Harry was shocked, but he responded by kissing her back for a few seconds, before realising what he was doing and pulling away.
"Angelina, what are you doing?" It wasn't that he didn't find her attractive, it was just that he'd only really kissed one girl before, and like everything involving Cho Chang, it hadn't gone well. He was completely clueless as to why she'd kiss him, when she could be with just about any other man in Hogwarts. He wasn't worth her time, and really didn't deserve her.
"Isn't it obvious?" She'd stopped kissing him, but was still holding him close. "Harry, you're an attractive guy, but you don't realise it. Half the witches in the school, including me, have a bit of a crush on you, and not because you're the Boy-Who-Lived. You're a good person, Harry. The fact that you're a true hero, and humble about it too, really helps."
Harry shook his head, still bewildered. "I'm no hero. I'm just Harry."
Angelina kissed Harry on the cheek. "That's why the girls love you, Harry. You don't take credit for, or boast about, your heroism. You are a hero, whether you want to be or not. You went after a troll in your first year, to save a girl you hardly knew. You went after a teacher who was trying to steal the Philosopher's Stone, even though you didn't know any real spells to stop him. You fought a basilisk without a wand, using the sword of Godric Gryffindor, one of the original Wizarding heroes. You were forced to compete in the Triwizard Tournament, against challenges designed for adult wizards, and won it. You're a star Quidditch player, one of the smartest in your year, and you managed to beat Voldemort several times. Tell me which part of that isn't true."
Harry blushed, and tried to stutter a response. "It ... it all sounds great when you say it like that, but it was mostly luck. I almost always had help, and I don't deserve credit for it all."
"No, Harry. You're incredibly modest, and that's one of your most attractive traits. No-one was with you when you killed the basilisk, or when you competed in each task of the Triwizard. I couldn't have done anywhere near as well as you did in any of the tasks, I'm ashamed to say."
Harry looked up at her, shocked, and shook his head. "Angelina, you'd have done way better than I did. I mean, you're amazingly smart, and pretty, and kind. You'd have figured out the clues faster, you'd have had better plans, and you're so much more powerful than I am."
Angelina smiled at Harry. "You seem to be quite a ladykiller too, Harry. Pay a girl compliments like that more often, and you'll be a very lucky bloke." She stood, helping Harry back up to his feet, and only then noticing his broken hand. "What did you do, punch a wall?"
Harry nodded sheepishly, and Angelina chuckled. "I've done that too, Harry. Let's just say I was going through a bad breakup, and got a bit mad in the corridor. Broke two fingers doing so, and it bloody hurt. Madam Pomfrey can help you heal it, if you'll come with me to the hospital wing." She held his non-broken hand as she walked him down the stairs, so he could begin to heal, in both body and mind.
AN: I always felt that Harry's Quidditch team-mates were under-used in the books and movies, so my fanfiction stories will quite likely have them play more of a role in them. I struggle to see why Harry wouldn't go to them for help training for the Triwizard Tournament, knowing that Angelina, Fred and George were all planning to enter anyway. Mind you, like most wizards, Harry seems to have very little logic. Otherwise, he'd have worked out that he was being manipulated by pretty much everyone.