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.
Watchfulness cleanses the conscience and makes it lucid. Thus cleansed, it immediately shines like a light that has been uncovered, banishing such darkness. Once this darkness has been banished through constant and genuine watchfulness, the conscience then reveals things hidden from us.
We must vigilantly guard our heart from unfitting thoughts and impressions, according to the word of the writer of Proverbs: ‘Keep thine heart with the utmost care; for out of these are the issues of life,’ (Proverbs 4:23).
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.
Your enemy, the evil one, the father of lies, does not slumber; and endeavors, by every means open to him, to harden your heart --- to make it false and crafty, to drive out from it faith and hope in God - together with love for Him and love and sympathy for your neighbor - and to occupy you with worldly, temporal interests. Watch yourself, watch the thoughts of your heart, and do not bind yourself in the chains of worldly desires and pleasures. Let your happiness be in the one God and the human soul.
Now you become angry and fainthearted and grieved, thinking that the heavenly Father is slow in answering. But I tell you that this will also happen as you desire—it will definitely happen—but first it takes prayer with all your soul, and then you must wait. And when you have forgotten your request and have ceased asking for it, it will come to you as a reward for your patience and endurance. When you reach the verge of despair while praying and seeking, then the fulfillment of your request is near. Christ wants to heal some hidden passion within you, and this is why He delays in granting your request. If you obtain it sooner, when you demand it, your passion remains uncured within you. If you wait, you obtain your request and the cure of the passion. And then you rejoice exceedingly and give warm thanks to God Who arranges all things in wisdom and does everything for our benefit.
This reading with prayer preceding strengthens the soul and gives it strength for the entire day. Doctors say you should not leave the house on an empty stomach. With respect to the soul, this is fulfilled by morning prayer and reading. The soul is fed by them, and sets out on the business of the day nourished.
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.
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.
No Christian believing rightly in God should ever be off his guard. He should always be on the look-out for temptation, so that when it comes he will not be surprised or disturbed, but will gladly endure the toil and affliction it causes, and so will understand what he is saying when he chants with the prophet: 'Prove me, O Lord, and try me' (Ps. 26:2 LXX). For the prophet did not say, 'Thy correction has destroyed me,' but, 'it has upheld me to the end' (Ps. 18:35 LXX).
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.
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...
We should zealously cultivate watchfulness, my brethren; and when, our mind purified in Christ Jesus, we are exalted by the vision it confers, we should review our sins and our former life, so that shattered and humbled at the thought of them we may never lose the help of Jesus Christ our God in the invisible battle.
We must accomplish the course of our earthly pilgrimage with the greatest attention and watchfulness over ourselves, unceasingly calling upon God in prayer for help.
The soul of all practices in the Lord is vigilance. Without vigilance, all these practices are fruitless. He who is desirous of saving himself must so establish himself that he might remain continuously vigilant toward himself, not only in solitude, but also under conditions of distraction, into which he is sometimes unwillingly drawn by circumstances.