A prayer offered while one has any cause to reproach a fellow man is an impure prayer. There is only one whom the praying person may and must reproach, and that is himself. Without self-reproach, your prayer is as worthless as it is while you are reproaching someone else in your heart. Perhaps you ask: How can one learn this? The answer is: One learns it through prayer.
You must set about rooting out the very desire to have things pleasant, to get on well, to be contented. You must learn to like sadness, poverty, pain, hardship. You must learn to follow privately the Lord's bidding: not to speak empty words, not to adorn yourself, always to obey authority, not to look at a woman with desire, not to be angry and much else. For all these biddings are given us not in order for us to act as if they did not exist, but for us to follow: otherwise the Lord of mercy would not have burdened us with them. If any man will come after me, let him deny himself, He said (Matthew 16:24), thereby leaving it to each person's own will-if any man will-and to each person's endeavor: let him deny himself.
Listen to the word of God handed down to you through the priest, & do as it teaches you; look upon the priest as the messenger of God; love him as your Father; care for him as he cares for you; do not believe calumnies about him & do not spread gossip; be not scandalized at his shortcomings, and pronounce no judgment; pray for him, for his duty is heavy & the forces of evil are raised against him; if he teaches without carrying out his teaching himself, remember the words of St. Matthew 23: 2,3.
Do not neglect the practice of the virtues; if you do, your spiritual knowledge will decrease, and when famine occurs you will go down into Egypt (Genesis 41:57, 46:6).