I keep returning to this question because I don't think it has one answer, and I've stopped trusting the people who give it one.
Some friendships end because of a single unforgivable thing. Most don't. Most just quietly stop being renewed, the way a subscription lapses — not from any decision, just from inattention on both sides.
A partial, unsatisfying list of reasons
- We wanted different things from the friendship and never said so
- Life put us in different rooms and we stopped choosing to leave them
- We changed, and the friendship was built for who we used to be
I don't think this is sad, exactly. I think it might just be what it costs to keep becoming someone.