Something has changed between you
For some people, something happened. A moment, a conversation, a disclosure that landed wrong, a silence that stretched past comfortable and then past recoverable. They have had the same conversation three or four times. It keeps ending in the same place. Neither person meant to be here. But here they are.
For others, nothing broke exactly. Life got in the way the way it does: one person had children, one moved, one changed, the friendship changed shape around all of it without anyone deciding it should. The friendship is still there. But something between them no longer fits the way it used to. The grief of that does not have a clear name. It is not a breakup. It is not a falling out. It is harder to explain than either of those things, and it does not go away on its own.
Either way, the friendship still matters. And what you have been doing by yourselves, the conversations you have had and the things you have tried to say, has reached the limit of what it can do from inside.
