You ask for some way of completely eradicating irritability. The inclination to irritability is given us to use against sin, and we were never meant to use it against our fellow men. When we do, we act contrary to our true nature.
He who chooses maltreatment and dishonor for the sake of truth is walking on the apostolic path; he has taken up the cross and is bound in chains (cf. Mt 16:24). But when he tries to concentrate his attention on the heart without accepting these two, his intellect wanders from the path and he falls into the temptations and snares of the devil.
In the beginning there are a great many battles and a good deal of suffering for those who are advancing towards God and afterwards, ineffable joy. It is like those who wish to light a fire; at first they are choked by the smoke and cry, and by this means obtain what they seek -- as it is said, 'Our God is a consuming fire' -- so we also must kindle the divine fire in ourselves through tears and hard work.
You are, I am sure, aware that for you penitence is now no longer limited to disclosing your sins to your confessor, but that you must now bear your sins in mind always, until your heart nearly breaks with their ugly load; and would break, were it not for your firm faith in the mercy of our Lord.
The Martyrs won Paradise through their blood; the Ascetics, through their ascetic life. Now you, my brethren, who have children, how will you win Paradise? By means of hospitality, by giving to your brothers who are poor, blind, or lame.
One should nourish the soul with the word of God: for the word of God, as St. Gregory the Theologian says, is angelic bread, by which are nourished souls who hunger for God. Most of all, one should occupy oneself with reading the New Testament and the Psalter, which one should do standing up. From this there occurs an enlightenment in the mind, which is in the mind, which is changed by a Divine change.
Remember always that, once we have decided consciously to strive after righteousness, we cannot escape catastrophes and sorrows, no matter where we are.
Pray simply. Do not expect to find in your heart any remarkable gift of prayer. Consider yourself unworthy of it. Then you will find peace. Use the empty cold dryness of your prayer as food for your humility. Repeat constantly: I am not worthy; Lord, I am not worthy! But say it calmly; without agitation.
One must by every means strive to preserve peace of soul and not be disturbed by offenses from others; for this one must in every way strive to restrain anger and by means of attentiveness to keep the mind and heart from improper feelings. And therefore we must bear offenses from others with equanimity and accustom ourselves to such a disposition of spirit that these offenses seem to concern not us, but others. Such a practice can give quietness to the human heart and make it as dwelling for God Himself.
If you refuse to accept suffering and dishonor, do not claim to be in a state of repentance because of your other virtues. For self-esteem and insensitivity can serve sin even under the cover of virtue.
The body is a slave, the soul a sovereign, and therefore it is due to Divine mercy when the body is worn out by illness: for thereby the passions are weakened, and a man comes to himself; indeed, bodily illness itself is sometimes caused by the passions.
Remember that a good action is always either preceded or followed by temptations. God permits this so that the virtue, exercised in that particular action, may be confirmed, consolidated, steeled.
Just as our Lord is solicitous about our salvation, so too the murderer of men, the devil, strives to lead a man into despair... Judas the betrayer was fainthearted and unskilled in battle, and so the enemy, seeing his despair, attacked him and forced him to hang himself; but Peter, a firm rock, when he fell into great sin, like one skilled in battle did not despair nor lose heart, but shed bitter tears from a burning heart, and the enemy, seeing these tears, his eyes scorched as by fire, fled far from him wailing in pain.
When the first order of angels fell from the angelic glory and became demons, the other nine orders humbled themselves and worshipped the All-holy Trinity, and remained in their place and rejoice forever. We, too, my brethren, must reflect what an evil thing pride is - that it cast down the devil from angelic glory and he will always burn in Hell - and that humility kept the angels in Heaven, and they rejoice perpetually in the glory of the Holy Trinity. Let us then, my brethren, avoid pride, because it is the first daughter of the devil, is a path that leads to Hell; and let us have humility, because it is angelic—it is a path that leads to Paradise.
