Please know that I own nothing written by J.K. Rowling. Thank you.
Catalyst
Lily Evans hadn't considered herself a responsible sort of person before coming to Hogwarts, though Peter Pettigrew doubted her claim. She had been the kind of girl to run towards the swings at any moment presented to her. She liked to stand while it swung, jumping off at the highest point. She'd played tag with the other kids and had tea parties with her older sister and did not-so-accidental magic with the boy who lived nearby. She had been anything but responsible before coming to Hogwarts.
"Things changed when my letter arrived. It couldn't be all fun and games anymore." She'd said during rounds with her Prefect partner, Remus Lupin. She thought about the family's reaction to the letter. How happy her parents had been that at last they'd found an explanation for the oddities that occurred around their youngest girl. How confused her sister, Petunia, had been at the first read through of Lily's letter, before turning angry that Lily wouldn't be going to school with her like they'd promised before. How upset Severus, the first magical person she'd known, had looked when he'd brought his letter to their park, and warning her that things might stop them from being friends at Hogwarts.
"Nothing has ever been as important as letting the people I care about know that I will always care about them." She'd whispered in a seemingly empty room to a well-hidden Sirius Black. It did and did not matter to her that those people doubted she'd keep her word. Petunia had all but stopped speaking to her following the attempt to show that being magic wasn't wrong. Severus only recognized her presence if they were alone. She'd be lying if she said the actions (or non-actions) of her two best friends actions didn't hurt, but she truly believed that if she stayed on their side as much as possible then eventually they'd stop cutting themselves off from her. They'd remember what they'd been like before Hogwarts and go back to being themselves.
"If I agree to this, I will never again be the person I was before knowing you." She cried when James Potter broke through her shields and asked her out on the November of their last Hogwarts year. Lily had tried her best to remain the girl she had been before Hogwarts, but too much had happened for her to be the girl who played dress-up on demand or preformed magic on others just for the sake of it. Too much had happened in the past two years. Petunia had blamed Lily for their parents' car accident just when Severus had called Lily the most derogatory of names in front of half the school. Peter had taught her all the popular wizarding world games while Lily studied werewolf lore and legislature on a whim. Remus came out of the Shrieking Shack to Lily the same summer Sirius ran to his best friends home.
James had changed, too. He'd held her, despite the discomfort of a crying girl. He'd apologized to her for the pressure he'd put of her friendship with Severus. He'd come to her for help when the people he cared about seemed to divide irrevocably. He smiled at her in thanks when Sirius came back to the dorm, when Remus kept his head high despite the Prophets destructive description of werewolves, and when Peter used the spell she'd taught him to repel his tormentors. He'd changed from an unaware jokester to a Head Boy that their class could count on to help.
"Lily Evans," he whispered while wiping away the tears from her cheeks. "The person you are, from before I knew you to now, is responsible for the situation we find ourselves. I wouldn't be me, if you hadn't been you. I wouldn't have fallen in love, if you had been something over than yourself. I wouldn't have become better, if we'd never spoken, if we'd never met. You are the catalyst for everything that has ever mattered in my life. I know it's a risk to go out with me, but I know if we just start that you will bring us all through."
"James Potter. I think that I would like nothing more than to visit Hogsmead with you."