Bridges don’t usually fail in one day. They rust from years of nobody checking. Same with friendships.

Collapse is almost always an accumulation nobody inspected. Nothing dramatic has to happen for a close friendship to stop being one: a few months of neither of you reaching out, two cancelled plans, a joke that landed badly and was never mentioned. Each of those is survivable on its own. Left alone long enough they add up to something that no longer holds weight.

Pick the friendship you have been coasting on and do the maintenance this week, which usually means a message with a date in it. Mention the thing that went slightly wrong rather than filing it away.