The follow excerpt is taken from a letter written by St. Paisius Velichkovsky to Schema-abbess Martha Protasieva, when the latter was going through a difficult spiritual struggle.
I write to your worthiness and beg and counsel you not to grieve overmuch or despair concerning the former trial and infirmity of your soul, but, with undoubting hope in God’s mercy, to place before God a true beginning of true repentance for the past infirmities, and to repent with your whole heart and soul and entreat forgiveness of His goodness; and He, being a God Who is good and loves mankind, rejoicing in your true repentance, as He has forgiven all sinners who have repented, will forgive you also all your transgressions, without any doubt.
It also comes to my mind, O Honorable Lady, that Christ the Saviour, our true God, when He wished to entrust the world to His chief disciples and Apostles Peter and Paul, so that they might preach in it His Gospel and by their preaching might instruct those who believed in Him in the true knowledge of God and the keeping of His commandments, and so that they might be merciful to sinners and the more easily forgive the transgressions of those who repent—by His Divine and unattainable decrees allowed that Peter should renounce Him three times and Paul should persecute and devastate His Church. And after Peter’s true repentance and Paul’s miraculous coming to believe in Christ, both of these Holy Apostles, inasmuch as they had known in themselves the weakness of human nature, were therefore most merciful, in the likeness of Christ the Lord, to those who transgressed and truly repented; and as they bore the burden of everyone on themselves, so also they inspired all to this, saying: bear ye one another’s burdens, and so fulfill the law of Christ (Gal. 6:2). Was it not somewhat in this fashion that Christ the Saviour, by His unsearchable decrees, allowed the above-mentioned trials and infirmities of soul to come upon you also, so that having beheld the more completely for a long time, as in a mirror, the infirmity of your soul and the weakness of human nature, you might learn to bear the infirmities of the weak and might be more inclined to have mercy on them in the spirit of meekness. Therefore, repenting before God, glorify His unfathomable Providence, which most marvelously ordains the salvation of those who fear Him and repent.
* This excerpt is from “Blessed Paisius Velichkovsky: The Man Behind the Philokalia” by Schema-monk Metrophanes