It had all started because of the D.A. meetings, or rather, because of Hermione. That was when he'd begun to feel less alone, like less of an outcast. He was finally part of something—as illegal as it might be. It was a known fact that Neville hardly displayed the greatly boasted about Gryffindor courage, but he personally felt it was something he'd grow into, becoming part of the D.A. was a step towards that courage.
It was in those very meetings that he became familiar with one Miss Luna Lovegood. It wasn't love at first sight—couldn't be they'd passed each other in the corridors often and had even shared a compartment in the Hogwarts' express. It was a welcome acquaintanceship, the nature of which evolved from an understanding of loneliness and doubt. It was small smiles shared in between classes and mealtimes. It was fleeting knowing looks when the looks in the eyes of one or the other became filled with sorrow. During the battle at the Ministry, true fear gripped at both of them. The only friends they knew were in danger, separated, outnumbered, and most importantly underqualified to fight against fully grown witches and wizards with expertise in the dark arts. Neville in particular was at the mercy of fear that day, with the torment of his parents' only feet away from him. When the entire ordeal was over with, everyone was badly shaken. Neville felt he needed to talk to someone about how he felt that night, about the cruelty of life, or really anything no matter how insignificant it was. He turned to Luna, who seemed to always be willing to listen. And though their conversation wasn't meaningful, it helped him to have someone so readily listen to his ramblings.
The D.A. helped them both find a safe heaven. It was there that they encountered the closest thing to friendship and acceptance. Both felt they lost something great when the D.A. was no longer necessary. Due to mutual feelings of loneliness the pair continued to spend time together, finding solace in each other's company. They grew closer as friends to the point of confiding in each other, and though Neville still found Luna to be a bit eccentric at times, it was more of an endearing quality. Throughout their many conversations they agreed to always be willing to help Harry out if he ever needed the D.A. again. So it came as no surprise to anyone when they were the only ones to answer the summoning the night Dumbledore died.
The grieving of Dumbledore was a sad but very rushed ordeal, and instead of drawing the two closer, it seemed to push them away. They would later blame their distancing on how very little time they had to process the death of a man most had revered (though in truth it was the fear of what the future held that made Neville wary around people during that time—and in turn that wariness made Luna give him the space she though he needed). Although their friendship remained, it was tentative, so when Ginny approached them with the idea of stealing the sword of Gryffindor from Snape's office both were just a tad reluctant to agree. So when there plan fell through the proverbial cracks and they were sent into the forbidden forest and Ginny laughed a forced laugh at their conjoined failure, Neville shared a meaningful look with Luna. They were both willing to put their safety on the line for what they believed. Turning to Ginny, Luna asked (her voice almost lacking its airy quality) if she wanted to start the D.A. again. The look of fear that flashed through the eyes of the youngest Weasley was gone so quick, Neville almost thought he'd imagined it. But her response was even quicker than the show of fear. Straightening her back with a renewed light in her eyes she said "I thought you two would never ask!" to which the pair only smiled.
It wouldn't be until later that Neville realized how much Luna had become a part of his life. By the time he realized how much her presence served to calm him it would be too late. When news reached him that she had been taken from the train, his heart dropped to his stomach. Guilt would try consuming him from there on out. If he had stayed with her maybe she wouldn't have been taken, but he had been trying to recruit new members for the D.A. and was sure it would only take him a few moments. Worry ate at him as no news of Luna came, and when the winter holidays ended and she wasn't back on the Hogwarts' express his distress was evident. Noticing his distress Ginny did her best to help, but she too didn't return after the Easter holidays. Neville felt so alone, and so guilty. His efforts to keep students safe and to continue the D.A. were re-doubled. There was no doubt in his mind that things would get better. He had not lost this much to those people to quit. But even he knew his limits, and eventually had to go into hiding. Even so hope came in many forms and in his case many students willing to fight for what they believed in.
The fear he carried every day dropped from his shoulders when he learned of Luna's safety. Still unaware of how deep his feelings really ran for the witch, he let a small smile play on his lips. She was okay. After many months of not having seen or heard of her, Neville finally got to see the witch. She looked smaller and frailer, and although her tone was still airy there was an edge to her eyes that hadn't been there before. It was clear that she had suffered and he was left to wonder how much because there was no time for meaningful conversations. There was barely time for stolen glances before the battle commenced.
Neville would never be able to properly say what happened during the battle. Everything was a blur of colors and bloodied bodies. The fear was palpable in the air, so thick one could almost taste it. There was no time to worry about anything but what was happening around you. With adrenaline coursing through his body, and wand work faster than he thought himself possible to accomplish Neville came out alive but very shaken. The emotions that had coursed through him throughout the battle ranged from fear to anger to sadness to pity and back again. To say he was exhausted was an understatement, but it was over and everyone left alive could rest easy.
He saw Harry slip off unnoticed just as the sound of the only voice he wanted to hear rang through his ears. That same voice was ringing in his ears now. As Neville focused on the present again his eyes caught those of Luna. Indescribable. The feelings coursing through his body were indescribable. She was a stunning sight in her vibrant green dress robes and intricately styled hair. She had ornaments—the names of which he couldn't name—hanging from both her dress and hair. She was barefoot and had a necklace made out of daisies. He was in love with this peculiar witch, and though his Gran had held reservations about their relationship he knew that she approved of their actions.
Having finished her vows, Neville began his. His promise to her was to protect her in every sense of the word, to cherish her and her individuality, to love and respect every aspect of her being, and to always remember that in her he had a partner, a wife, a shoulder to lean on when need be, but most importantly a beloved friend.
With the ceremony over, he took another moment to admire the great person that was his Luna. Looking up to his eyes, she gave him a small smile, one she reserved for his eyes only. His heart swelled at the moment the shared. Pulling her closer to him, he rested his chin on her head and inhaled deeply. She was his home, his support, his best friend—as he was hers—he knew that no matter what life threw his way he'd be fine so long as his beloved is by his side.