"Therefore, if you are offering your gift at the altar and there remember that your brother has something against you, leave your gift there in front of the altar. First go and be reconciled to your brother; then come and offer your gift."1
Psychologists tell us that half the adult population is still harboring unresolved negative feelings towards their parents. They also warn us that until these relationships with our family of origin are resolved (and with any other significant person), we can never fully cultivate any other loving and healthy relationship. Unresolved conflicts from the past contaminate every relationship we have in the present. They can and do also seriously affect our physical and spiritual well-being.
Sometimes reconciliation isn't possible because that is dependent on both parties. However, it is imperative that we take care of our side of any conflict and resolve any feelings of hurt and anger we might have so we can genuinely forgive any and all who have hurt us. To fail to forgive keeps us bound by the past. And as noted before, "Failing to forgive is like drinking poison and waiting for the other person to die."
It's not without good reason that Jesus taught us the need to forgive even our enemies even to seventy-times-seven (meaning endlessly). He also said that if you come to God and there remember you have an impaired relationship with a brother or sister, leave your gift for God for the time being and do everything in your power to resolve that relationship.
Suggested prayer: "Dear God, please confront me with the reality of any significant impaired relationship that I have—and give me the courage to do what I need to do to resolve my part in this conflict. And help me to forgive any and all who have ever hurt me so that I am freed to fully live and fully love—and to experience the depth of your forgiveness. Thank you for hearing and answering my prayer. Gratefully, in Jesus' name, amen."