1. There should always be a sense of closure or clarity as to why it happened so that you can move cleanly into your next phase.
2. It just so happened that he started liking me and I started liking him.
3. it so happened that
3. It happened so long ago, but that doesn't mean that it's over.
4. It has happened so many times that many people simply take it as a joke.
5. Although the intervening decade seems to have passed in the blink of an eye, so much has happened that it feels like a lifetime.