Disclaimer: I own nothing.
A/N: This is my first shot at a full on romance, so hopefully it won't be a total disaster. So, here goes nothing. Enjoy!
When he first saw her, she was with that small and rather greasy little boy, Severus Snape. He and Snape hated each other immediately. Someone told you opposites attract? They were wrong. At least in this case. He had made a great friend in Sirius, and he had met the girl he would love for the rest of his life. He didn't love her then of course, but he was inexplicably drawn to her. Though he didn't show it, he was rather disappointed when she flounced off with Snivellus. But still, he had his friends, and he was sorted into the house he always wanted to be in, and so was she.
The next time she snubbed Sirius' offer of a seat. A cloud passed over his sunny mood at being sorted into Gryffindor with his friends. And he still wasn't sure why. He was only eleven. He would find out soon. A cloud went over his mood quite regularly that year, as Lily refused to have anything to do with him, saying he was an arrogant bully.
He noticed as he went into his second, third and fourth years at Hogwarts, he was drawn to her more and more. He now understood why, he was in love with her. He could, quite feasibly, have gone out with pretty much any other girl in the year, and they certainly sighed and giggled over him more and more as time went on, but he only had eyes for her. She still disliked him, though he noted happily she got on less with Snivellus these days.
In their fifth year, she started trying to hide small smiles at his pranks. The smiles were almost imperceptible, but they were there. When he cursed and levitated Snivellus after the DADA O.W.L, she found it harder to hide her smile. She was still angry of course, but more with Snape than him after he called her a Mudblood and strode away, claiming she would rather go out with the Giant Squid. "Reading between the lines, I'd say she thinks you're a bit conceited, mate" Sirius had said. Well, maybe it was time to change a little. In the meantime, there was Snivellus to hex.
Later, he found out she had distanced herself from Snape. His heart leapt when he heard the news, though he couldn't help but feel an almost imperceptible stab of pity for Snivellus. He shook his head and the moment passed. Why would he feel sorry for Snivellus? He was a Dark arts obsessed oddball, who seemed never to wash. He was everything James hated, and the hatred was mutual. But still...
She reciprocated his love in the 7th year, when, as Sirius and Remus put it, he deflated his head a bit. They were happy. They married young, as many did in those days. Some of those marriages were panicked misjudgements, but not his and Lily's. On his wedding day, staring into her eyes, he was certain that he was the most fortunate man alive. Sirius made what was only a slightly embarrassing speech, if only because Lily had threatened to hex him if he wasn't careful. They argued, but it was a friendly banter sort of argument, which they both enjoyed.
He was happiest when his son was born. Harry James Potter. His father's face and his mother's beautiful eyes, and an air of mystery from somewhere else entirely.
That fateful Halloween night, when he saw Voldemort, he knew he stood no chance, especially without his wand. But he was a Gryffindor, brave and proud, and he would do anything to protect his beloved wife and son. Unfortunately he couldn't. Bravery is a poor shield against the killing curse of all things. His spirit watched, agonised, as she died, but was relieved that his son survived. As they passed on, they saw Hagrid and Sirius looking after Harry, talking, then coming to an agreement, and Hagrid flew off on Sirius' bike. They were together and their son was safe. That was all that mattered to James Potter. That was all that had ever mattered.