When I first start out in a fandom, it's all about the first times. Trying to see how the characters fit together, trying to find a rationale, the basis of a manifesto for Their Love.
For Sam and Gene, in those early days, it was about trying to find all of the different combinations in which they could fit together (and there's a few, which is refreshing.) It kind of went: punchy violent denial and wilful misunderstanding, punchy unmistakeable and unremarked upon attraction, punchy sex-against-filing-cabinets, punchy arguments and understanding, bantery camaraderie (with a possible punch or two.) I've noticed my mind tends to class them in this sort of hierarchy --- that in order to 'get' them, I had to go through the violent denial and angst stage first. I'm eminently jealous of people who didn't.
From there my mind wanders into established relationship. The characters have found their positions, they've made it over obstacles, they've had those conversations necessary for a relationship to work. In my head, they're established relationship. I know how they fit together now. But this is where a problem arises --- I still write first time fic --- and I sometimes forget to do all the background in the story.
So. Now that I've figured this out, I can work on not doing this in future. Justification for actions, wooo! \o/