Bury the Hatchet
The phrase "bury the hatchet" originated with the American Indians. When two chiefs came to a peace agreement, they would literally bury a hatchet in the ground. A sense of finality and lasting impact.
Perhaps there is someone from your past where the relationship came to an unfortunate end. An irreconcilable difference or something worse, whatever it was, the effort or pain to redeem the past has seemed too much. So, we attempt to forget the person who was once a friend and pretend there's no answer to the problem.
But, life is short, and that person or relationship is worth one more attempt to "bury the hatchet." You'll never regret mending a broken relationship, but you will regret never trying.