Hmmm. The problem is that a lot of the *why* has to do with the people that we were then. And I'm not sure I could adequately describe that to you, since I was inside of it. I can say that we had more shared interests at the time--now, we have shared meta-interests. We always did have our own things going on--that's probably part of it too. Allowing the other to have his/her own personhood independent of the relationship, instead of insisting on two halves of one thing.

I know, this doesn't really answer the question, but I have never been good at huge umbrella vagueness. Specifics, I can answer. Generalities, not so much.