Sometimes you come to the realization that there are simply things which you have to accept.
This tears at the fabric of our societal understanding, of course. We have been taught that we are able to make our own fate, to chart our own course, to turn any situation or circumstance into the one that we desire. In fact, I would go so far as to say that it is almost considered a failure to not be able to do such a thing.
But sometimes, the reality is that some things simply cannot change.
Some of these things depend on circumstances beyond our control, things which we can neither directly nor indirectly impact. Some of these depend on people who will not change, not have we the power within us to make it so.
Either way, the initial realization can be a crushing blow - after all, we interpret the failure to be something caused of our own inabilities, of our weaknesses, of our lack of trying. We may try to fight this blow by redoubling our efforts. And perhaps then we try to go to the other side of ignoring the situation, or even acting out against it. Perhaps we may sink into a depression over it.
And then, one day, we learn to accept it.
Acceptance does not change it, of course. The situation is still the same. The relationship is still not what we wanted it to be. But in acceptance comes the ability to move on.
Maybe the thing will not change. But let it not be an anchor to weigh us down in the rest of our life.