I think a person should simply learn to let go, as difficult as it might be. The world is a very large place and people we interact with at one point in our lives are often long gone at another.
To insist on a subjective and elusive idea of “fairness” is to set one’s self up for disappointment. It’s far better in the long run to let go and move on.
I think that’s the idea behind the tefilah zaka, customarily recited erev Yom Kippur.