Mercy Comes from Mindfulness
Relationship issues involve two parts. Your part and someone else's part. You can only "grow" in mercy, humility, and kindness on your end. The other person must also grow for healing to take place.
Let go of the past, the mistakes, the drama, the sadness, and embrace the people that you are traveling with...sometimes someone steps off the train of life unexpectedly, and you do not have the opportunity to make things right between you.
Peace is the most important thing, not who was right and who was wrong.