Disclaimer: The Harry Potter Universe belongs to J. K. Rowling.
It's a well-known fact that closing your eyes, and pressing your fingers against them, will cause what looks like sparks of light to shoot across your vision. Many people have tried this, and some have even gone so far as to experiment with different levels of pressure, to see if there were variations in the lights.
Harry Potter was a connoisseur of what he called Personal FireFlashes. After all, when locked up in a dark cupboard, there's not a lot to do that involves eyes. He had cataloged no fewer than seventeen different types of Personal FireFlashes, and could reproduce most of them reliably. He had even named them, although their names wouldn't mean a whole lot to anyone else, as they were based on the feelings evoked in his mind upon seeing them.
Number 16, also known as PondSwimming, was the best, he thought. It involved a kind of paisley-shaped greyness, with orange and red sparks outlining the grey. Number 3, on the other hand, he tried never to get. It consisted of a green hue with intermittent flashes of red that instantly brought back indistinct memories of fear and pain and screaming. He had named that GreenScreamHorror, and even the thought of it caused him to shudder and open his eyes wide.
The first time he saw anything remotely similar to his Personal FireFlashes, was one evening when the Dursleys had gone out to celebrate Bonfire Night, and had forgotten to lock his cupboard door. He had snuck out and turned on the telly, and there, on the news, were the most amazing explosions and sparks and flames in the sky. He was entranced, and watched for far too long, as the telly was still warm when the Dursleys came in. Hiding, quaking with fear in his cupboard, Harry resolved two things: the first was to never watch the telly more than half an hour while the Dursleys were gone, and second, that he would one day see fireworks, as he now knew they were called, live and in-person. That evening, as he prayed that Vernon wouldn't think to feel the television to see if Harry had been stealing electricity, he came up with 7 more types of External Fireworks to add to his list, now mentally renamed FireFlashWorks.
The world of magic held a vast array of wonders for Harry. Intelligent pets, instantaneous travel, odd-smelling liquids that did strange things to one's insides, and rather outdated wardrobes. But the thing that most entranced him were magical Fireworks. Dr. Filibuster's Fabulous Wet-Start No-Heat Fireworks gained legendary status on Harry's list. Fred and George had introduced him to that most wonderful of inventions, and almost immediately thereafter, Harry had decided that, backward as the society was, any group of people that could produce such wondrous spectacles deserved to prosper. The FireFlashWorks list now numbered 36.
But, as wonderful as Dr. Filibuster's Fireworks were, they had to take a back seat to Weasleys' Wildfire Whiz-Bangs. The final exit of the Weasley twins from Hogwarts gave Harry many nights of contemplation and categorization as his list grew to 41.
Harry thought that he'd most likely plumbed the depths, or perhaps scaled the highest peaks, of Fireworks--at least, insofar as noting them on his list. It was getting slightly difficult to remember the order, although the first 17 remained ingrained forever, and, even now, he knew exactly how to reproduce each one. It was the more external type that seemed to be muddling up in his brain, and he eventually decided that he'd just have one simple category for each. Thus, number 18 was entitled MuggleBonfireWorks, and was remembered fondly, albeit vaguely. Number 19 was, of course, FilibusterPhenomenal. And number 20 was ever after referred to as UmbridgeEliminationBangs.
As Ginny's lips contacted Harry's for the first time, something he had been hoping for for most of the year, Harry felt something inside himself that he'd never experienced before. Of course, he could reproduce FireFlashes in his vision by carefully varied pressure, but this--this encompassed his whole body, making it feel as if the best of FilibusterPhenomenal and UmbridgeEliminationBangs were holding court to see which could outdo the other.
Walking on the grounds with his new girlfriend, holding her and watching the Giant Squid in the lake, exploring broom closets and finding ever-more-inventive locations to utilize an Invisibility Cloak served to add more items to the FireFlashWorks. Number 21 was QuidditchKissSparks. Number 24 was QuietDayLove. And, perhaps the best one of all was Number 27, FlowingLoveFire.
The year away from Ginny was torture. Watching Ginny's dot on the Map, and remembering certain of the items on the list, especially the last set, were the only pleasures he could find. As the final showdown approached, however, it became harder to remember numbers 21 through 27, and much too easy to think of number 3. That was probably prophetic, perhaps the only Divination that Harry had ever done successfully, as Harry had to go through the greatly undesired reliving of a very physical GreenScreamHorror.
The day after the Final Battle, however, Ginny helped him add number 28, AliveFreeExultationReunion.
Harry was incredibly nervous. He wasn't fearful, except for the very real possibility of losing the contents of his stomach before the ceremony could even start. He was just . . . excited, and scared, and happy, and apprehensive. He was finally able to control his nerves by reciting the names of all 28 FireFlashWorks and reviewing how to produce them, although he tended, once again, to skip number 3. Someone came to get him, and position him, and he managed to keep his calm, until he saw Ginny, walking down the aisle toward him, with a smile so radiant that he instantly added number 29, GinnySmileWife.
Harry's list had kept him sane in stressful times, it had been a constant companion as he coped with everything that was forced upon him. It had, perhaps, helped to define his life and progress. It commemorated some of the happiest, and some of the saddest, times of his life, and he had believed that it would stay with him forever, allowing him to chronicle more of the highs and lows of life. But then came the wedding night . . .
Neither Harry nor Ginny knew exactly what they were doing, although both had been given The Talk. But with many kisses, and touches, and soft laughter, and sighs and gentlenesses, they worked it out. And the love between the two exploded and consumed them both, and they fell asleep together, entwined in heart and mind and body. And the next morning, Harry's list of FireFlashWorks had been demolished, devastated, razed to the ground. There were only two categories left: GinnyLoveForever and EverythingElse.