The Bowlby conjecture states that we were designed to operate within a social network of about 150 individuals. And while there were changes to that group (births, deaths, the rare individual joining or leaving the tribe), it was overall stable. The relationships you made as a child were the same ones you had throughout your life. Your interactions with each person were strung together in an ‘infinite game” where there is always another encounter after the current one, and one after that, and so on.
Another name for this is the iterated prisoner’s dilemma (but I prefer the term “cooperation dilemma”). In our modern society, it is possible to uproot yourself and move to a new community severing ties with your old one, and no one really looks askance at that. It's common. But it enables people to never learn the emotional skills necessary to work through conflict and injuries, which is essential in building long-term healthy relationships.
In our ancestors’ world, the constraint of needing to be a member of a tribe to survive and thrive essentially forced everyone to work towards a resolution. Of course in extreme cases, the resolution might be banishment or death, but the vast majority of the time, it meant both sides shared, made amends, healed, got to closure, and moved on. Our social emotions exist for a very important reason: they bind the tribe together, and push us towards reconciliation when there is damage in the relationships.