"We implore you, in Christ's name: be reconciled to God!" (2 Cor 5:20) God the Father so strongly desires that we be reconciled to Him that He sent His Son to die for us (Rm 5:10) and thereby "reconcile everything in His person" (Col 1:20).
God the Father insists that we be reconciled not only with Him but also with our brothers and sisters in Christ. In the Sermon on the Mount, Jesus stated: "If you bring your gift to the altar and there recall that your brother has anything against you, leave your gift at the altar, go first to be reconciled with your brother, and then come and offer your gift" (Mt 5:23-24). Without reconciliation, our prayer backfires on us, God does not forgive our sins (Mt 6:12), our relationship with Him deteriorates, and we are lost and doomed to the everlasting alienation of hell. Therefore, "in Christ's name, be reconciled!" (2 Cor 5:20)
"If your brother should commit some wrong against you, go and point out his fault, but keep it between the two of you" (Mt 18:15). If you have disobeyed this command of the Lord by telling someone about what someone else did against you, repent, apologize to the person for talking behind his back, then point out the person's sin. This first attempt at reconciliation works most of the time because of the power of Jesus' reconciling, sacrificial death. If necessary, make the other three attempts at reconciliation referred to in Matthew 18:16-19. Do all that you can to be reconciled now.