Abba Or used to say this, 'Do not speak in your heart against your brother like this: 'I am a man of more sober and austere life than he is,' but put yourself in subjection to the grace of Christ, in the spirit of poverty and genuine charity, or you will be overcome by the spirit of vainglory and lose all you have gained. For it is written in the Scriptures: 'Let him who stands take heed lest he fall.' (I Corinthians 10:12) Let your salvation be founded in the Lord.'
If you have spoken evil of your brother, and you are stricken with remorse, go and kneel down before him and say: 'I have spoken badly of you; let this be my surety that I will not spread this slander any further.' For detraction is death to the soul.
When it is painful to remember the past, it is better to simply repent of what had been bad, and think no more about it. In order not to despair or be enfeebled by it, 'remember the examples of God's great mercies to great sinners. The main thing: do not condemn, do not envy, know yourself and be with God.'