Friendship is voluntary family without inherited obligation.

Friendship has the closeness of family without the obligation, which makes it both freer and more fragile. Nobody has to stay, which means the presence of the people who do stay means something a legal or biological tie cannot mean. It also means nothing keeps it alive except choice, repeated. That is the whole arrangement and the whole risk.

Since nothing external holds it together, be deliberate about the choosing. Put the meeting in the calendar, make the trip, send the message you keep meaning to send. Voluntary bonds die of neglect rather than conflict.