“Go first to be reconciled with your brother.”
Nobody will be able to obtain anything at all through prayer if he does not pray in a good frame of mind and with sincere faith… It is not a question of talking a lot… Rather, it has to do with coming to prayer with a soul that is troubled by resentment. We can’t imagine that someone comes to prayer without having prepared his heart; we also can’t imagine that the person praying might obtain forgiveness of his sins if he hasn’t first forgiven with all his heart his brother, who is asking forgiveness of him …
So first of all, the person who is preparing to pray will be at a great advantage if he adopts an attitude which helps him to place himself in the presence of God and which helps him to speak to God as to someone who sees him and is present to him. Certain images and memories of past events clutter the mind, which lets itself be invaded by them; thus, it is useful to remember that God is present and that he knows the most secret movements of our soul. Then the soul will prepare to please the one who is present, who sees it and who anticipates all its thoughts, the one who searches the heart and probes the soul (Ps 7:10)…
As Sacred Scriptures say, the person who prays must lift up pure hands; he must forgive each one of those who have offended him, reject everything that troubles his soul and not be annoyed with anyone… Who can doubt that this state of the soul is the most favorable? Paul teaches this when he says in his first letter to Timothy: “It is my wish, then, that in every place people should offer prayers with blameless hands held aloft and be free from anger and dissension,” (1 Tim 2:8).
St. John of the Cross