The enemy constantly endeavors to awaken in the abyss of the human heart a great turmoil about trifles. This is one of his tricks to blind our soul to the sun of truth, Christ our Lord, hidden in the heart's core of every one of our neighbors.
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.
Faith is truly a gift, gained for us through Christ's advent. But this does not abolish our freedom or responsibility. God desires of us not only faith but action too.
God smiles on the compassionate heart. Every time a beggar knocks at your door, try to perceive Christ Himself under the humble disguise. Would you, under any circumstances, let Christ knock in vain? The moral qualities of the individual beggar have nothing to do with it; that is Christ's concern, not yours. Who are you to judge your brother? Christ is using the beggar’s hand and mouth to test your compassion of Himself. Will you fail Him?
Fasting needn't be limited to abstinence from food alone, because true fasting is departure from evil deeds. Forgive your neighbor any insult, abstain from causing your neighbor offence, abstain from irritation, from senseless sorrows, from fear, wrath, and so on. ‘True fasting is alienation from evil, temperance of the tongue, setting aside of wrath, casting out of lust, idle talk, lies, and oath-breaking’…This is a true and pleasing fast for the Lord. Departing from these vices and from a corrupt state is what comprises a true fast.
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.
Do not attempt to assess the quality of your prayer. God alone can judge its value. To us, our own prayer must always appear so poor an effort, so inadequate an achievement, that the cry of the publican spontaneously rises from our lips.
I always sought out the Divine Writings, above all, the laws of God and their explanation of them by the Fathers, and the apostolic traditions, then the lives and the teachings of the Holy Fathers, and I gave my whole attention to these and so gradually learned. In them I lived and breathed...and if there was something to do to improve myself, and if I did not find it immediately in the Holy Writings, I laid it aside until I could find some teaching on this point.
The best medicine for pride, man’s greatest sickness of soul, is humility. Words cannot describe or explain it, but the Fathers say that he who strives hard to live according to the precepts of our Lord, and is fully aware of his own sins, acquires it steadily. Therefore be very careful never to think yourself good, or the least bit better than others.