Our soul is simple as thought, and rapid as thought or lightning. In an instant it can be wounded by sin and become attached to corruptible things; in an instant it can fall away from the love of God and its neighbor through a single unrighteous thought, through a single passionate desire, through a single malevolent thought, and, therefore, we must constantly watch our heart, lest it should incline to words or thoughts of evil, and must ever strive to preserve it in God's simplicity and purity, and in the love of God and its neighbor.
Imagine, picture the multitude of your sins and imagine how tolerant of them is the Master of your life, while you are unwilling to forgive your neighbor even the smallest offense. Moan and bewail your foolishness, and that obstruction within you will vanish like smoke, you will think more clearly, your heart will grow calm, and through this you will learn goodness, as if not you yourself had heard the reproaches and indignities, but some other person entirely, or a shadow of yourself.
Truth is the foundation of everything that has been created. Let truth be also the foundation of all your works (both inward and outward), and especially the foundation of your prayers. Let all your life, all your works, all your thoughts, and all your desires be founded upon truth.
Both public and private prayer are necessary in order that we may lead a truly Christian life, and that the life of the spirit should not become extinct in us. It is indispensable that we should attend divine service in church with faith, zeal and understanding, just as it is indispensable to provide a lamp with fuel or power if it is to burn and not to go out.
There is nothing more efficacious against the wiles of the devil, dearly beloved, than the kindness of forgiveness, and the bountifulness in charity, by means of which sin is either avoided or overcome.
Man's chief aim should be to find God. In finding God, he finds true happiness. The interior prayer we have been discussing [the Prayer of Jesus] leads man to Him. We can never thank God sufficiently for revealing Himself to us. We can never even thank Him enough for the other goods He bestows upon us. God need not have created man: He had hosts of angels. Yet He created man and countless marvelous things for him.
The man of Christ embarks upon the path of divine perfection by overcoming, with the aid of evangelical virtues, the sin and evil within him and in the world around him. He constantly marches on from one good to another, from smaller to greater, from greater to greatest. In this progress he never pauses, for any delay would bring spiritual stagnation, numbness, death. Through every pure thought, every holy sentiment, every good desire and kindly word, he progresses toward resurrection, immortality, eternal life.
The evil spirit tries to scatter prayer as if it were a sand heap, tries to turn the words into dry sand, without coherency or moisture - that is to say, without fervor of heart. Thus prayer may become either a house built on sand or a house built on a rock. Those build on sand who pray without faith, absently, coldly: such prayer is scattered of itself, and does not bring any profit to him who prays; those build on a rock who, during the whole time of their prayer, have their eyes fixed upon God, and pray to Him as to a living person, conversing face to face with them.
He who seeks grace from God must, above all, endure temptations and afflictions no matter how they come. Otherwise, if he becomes indignant and doesn't show enough patience during temptation, neither will grace manifest itself, nor will his virtue be perfected or will he be counted worthy of any spiritual gift.