Apostolic teaching, Beloved, exhorts us that we put off the old man with his deeds (Eph. iv. 22; Col. iii. 9), and renew ourselves from day to day by a holy manner of life. For if we are the temple of God, and if the Holy Spirit is a Dweller in our souls, as the Apostle says: You are the temple of the living God (II Cor. vi. 16); we must then strive with all vigilance that the dwelling of our heart be not unworthy of so great a Guest.
Do not be surprised that you fall every day, do not give up, but stand your ground courageously. And assuredly, the angel who guards you will honor your patience. While a wound is still fresh and warm, it is easy to heal; but old, neglected and festering ones are hard to cure, and require for their care much treatment, cutting, plastering and cauterization. Many from long neglect become incurable, but with God all things are possible.
The heart which is constantly guarded, and is not allowed to receive the forms, images and fantasies of the dark and evil spirits, is conditioned by nature to give birth from within itself to thoughts filled with light. For just as coal engenders a flame, or a flame lights a candle, so will God, who from our baptism dwells in our heart, kindle our mind to contemplation when He finds it free from the winds of evil and protected by the guarding of the intellect.
Watch constantly, learning to understand God's law, for this warms the heart with heavenly fire. Guard your lips from the idle word, or empty talk, lest the heart gets used to evil words.
It is impossible for the soul to attain anything spiritual and pleasing to God, or to be free of inner sin, without guarding of the mind and purity of heart, in other words, without sobriety... If with God's help we gain something daily through our sobriety, we should take care not to enter into communication with other people without discrimination, lest we suffer loss through our converse with them and are led into temptation.
If we cut off the causes of the passions for only a short while, and occupy ourselves with spiritual contemplation without making it our sole and constant concern, we easily revert to the passions of the flesh, gaining nothing from our labor but theoretical knowledge coupled with conceit. The result is a gradual darkening of this knowledge itself and a complete turning of the intellect towards material things.
When someone is beginning the spiritual life, he should not study a lot, but instead watch himself and guard his thoughts. A strong person is the one who chews well, not the one who eats a lot.
If the saints, who had attained passionlessless, had to be vigilant over themselves so as not to fall from their state of grace - then all the more is daily attentiveness and concern over our eternal salvation necessary for us sinners. The fact that we are still alive means that the Lord patiently endures our sins and awaits our amendment, and if someone lawfully labors for his salvation, the Lord takes him at a time when he becomes worthy of God’s mercy.
Continually take careful note of your inner intention: watch carefully which way it inclines, and discover whether it is for God and the sake of goodness itself and the benefit of your soul...