If you have received from God the gift of knowledge, however limited, beware of neglecting charity and temperance. They are virtues which radically purify the soul from passions and so open the way of knowledge continually.
Unless curbed by the fear of God that accompanies the practice of the virtues, spiritual knowledge leads to vanity; for it encourages the person puffed up by it to regard as his own what has merely been lent to him, and to use his borrowed intelligence to win praise for himself. But when his practice of the virtues increases concomitantly with his longing for God, and he does not arrogate to himself more spiritual knowledge than is needed for the task in hand, then he is made humble, reduced to himself by principles which are beyond his capacity.
A man may seem to be silent, but if his heart is condemning others, he is babbling ceaselessly. But there may be another who talks from morning till night and yet he is truly silent, that is, he says nothing that is not profitable.
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.
There are three things that impel us towards what is holy: natural instincts, angelic powers and probity of intention. Natural instincts impel us when, for example, we do to others what we would wish them to do to us (cf. Luke 6:31), or when we see someone suffering deprivation or in need and naturally feel compassion. Angelic powers impel us when, being ourselves impelled to something worthwhile, we find we are providentially helped and guided. We are impelled by probity of intention when, discriminating between good and evil, we choose the good.
It is not food that is evil but gluttony; not childbearing but fornication; not money but cupidity; not glory but vainglory. If this be so there is no evil in anything that is, except wrong use, which results from our mind neglecting to cultivate our nature (the powers of the soul, and their right direction).
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.
According to the teaching of the Fathers, any impression which, touching the heart, fills it with a great irritation, must come from the region of passions. Therefore impulses which spring from the heart should not be followed at once, but only after careful examination and fervent prayer. God preserve us from a blind heart! It is well known that passions do blind the heart and screen the shining sun of the mind that we should all strive to gaze at.
Just as the human word which proceeds naturally from the mind is messenger of the secret movements of the mind, so does the Word of God, who knows the father by essence as Word knows the Mind which has begotten it (since no created being can approach the Father without Him), reveal the Father whom He knows. As the Word of God by nature, He is spoken of as the 'messenger of the great plan of God'.
A man of good sense, realizing how beneficial are the judgments of God, thankfully endures the tribulations they bring him, holding none guilty but his own sins. But a foolish man, when he sins and is punished, regards as the culprit of his ills either God or men, not discerning the wisdom of Divine Providence.
Love and self-control free the soul from passions; spiritual reading and contemplation deliver the intellect from ignorance; and the state of prayer brings it into the presence of God Himself.
Since self-love is the origin and mother of evil, when this is eradicated all the things which derive from it are eradicated as well. For when self-love is absent, not the slightest trace or form of evil can exist in any way at all.
Meekness and humility of heart are virtues without which it is impossible to inherit the Heavenly Kingdom, to be happy on earth, or to experience inner calm.
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.
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 condemn today as base and wicked the man whom yesterday you praised as good and virtuous, changing love to hatred, because he has criticized you, but even though you are still full of resentment, commend him as before, and you will soon recover your same saving love.