There is one method which, if practiced with full attention, will seldom allow anything passionate to slip unnoticed into the heart. This is to examine our thoughts and feelings, so as to discover which they tend: towards pleasing God or towards pleasing ourselves.
Even a pious person is not immune to spiritual sickness if he does not have a wise guide -- either a living person or a spiritual writer. This sickness is called prelest, or spiritual delusion, imagining oneself to be near to God and to the realm of the divine and supernatural. Even zealous ascetics in monasteries are sometimes subject to this delusion, but of course, laymen who are zealous in external struggles (podvigi) undergo it much more frequently. Surpassing their acquaintances in struggles of prayer and fasting, they imagine that they are seers of divine visions, or at least of dreams inspired by grace. In every event of their lives, they see special intentional directions from God or their guardian angel. And then they start imagining that they are God's elect, and often try to foretell the future. The Holy Fathers armed themselves against nothing so fiercely as against this sickness -- prelest.
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.
What do we do when attacked by some criminal? We strike out at him and shout for help. Our cries are answered by the police, who then rescue us from danger. We must do the same in inner warfare with the passions. Filled with anger against them, call for assistance: Help me, O Lord! Jesus Christ, Son of God, save me! O God, make speed to save me! O Lord make haste to help me! Having thus called on the Lord, do not allow your attention to wander from Him, do not let it turn to what is happening within you, but go on standing before the Lord and imploring His help. This will make the enemy run away as though pursued by flames.
To act 'according to one’s strength' means to use a little less than necessary both of food, and drink, and sleep... As for food, restrain yourself when you wish to eat a little more, and in this way you will always make use of it moderately.
The kingdom of God is within us when God reigns in us, when the soul in its depths confesses God as its master, and is obedient to Him in all its powers. Then God acts within it as master ‘both to will and to do of his good pleasure’ (Phil. ii. 13). This reign begins as soon as we resolve to serve God in our Lord Jesus Christ, by the grace of the Holy Spirit. Then the Christian hands over to God his consciousness and freedom, which comprises the essential substance of our human life, and God accepts the sacrifice; and in this way the alliance of man with God and God with man is achieved, and the covenant with God, which was severed by the fall and continues to be severed by our willful sins, is re-established. This inner alliance is sealed, confirmed, and given the strength to maintain itself by the power of grace in the divine sacrament of baptism, and for those who have fallen after baptism, in the sacrament of repentance: and afterwards it is constantly strengthened by holy communion. All Christians live thus; and consequently they all bear the kingdom of God within themselves, that is to say they obey God as King and are ruled by God as King.
The spirit of faith and piety of the parents should be regarded as the most powerful means for the preservation, upbringing and strengthening of the life of grace in children.
He who is afraid of God's punishment has a slave-like fear of God, and it is this that makes him refrain from evil: 'Out of fear of the Lord men shun evil' (Prov. 16:6. LXX)... through fear of what threatens us we sinners may be led to repent and may seek deliverance from our sins...The more a man struggles to do good, the more fear grows in him, until it shows him his slightest faults, those which he thought of as nothing while he was still in the darkness of ignorance. When fear in this way has become perfect, he himself becomes perfect through inward grief: he no longer desires to sin but, fearing the return of the passions, he remains in this pure fear invulnerable. As the psalm puts it, 'The fear of the Lord is pure, and endures for ever' (Ps. 19:9. LXX). The first kind of fear is not pure, for it arises in us because of our sins. But, independent of sin, the person who has been purified continues to feel fear, not because he sins, but because, being human, he is changeable and prone to evil. In his humility, the further he advances through the acquisition of the virtues, the more he fears. This is natural; for everyone who possesses wealth greatly fears loss, punishment, dishonor, and the consequent fall from his high estate...The sign of the first kind of fear is hatred of sin and anger towards it, like someone wounded by a wild beast. The sign of perfect fear is the love of virtue and the fear of relapsing, since no one is unalterable.
We ought all of us always to give thanks to God for both the universal and the particular gifts of soul and body that He bestows on us. The universal gifts consist of the four elements and all that comes into being through them, as well as all the marvelous works of God mentioned in the divine Scriptures. The particular gifts consist of all that God has given to each individual. These include wealth, so that one can perform acts of charity; poverty, so that one can endure it with patience and gratitude; authority, so that one can exercise right judgment and establish virtue; obedience and service, so that one can more readily attain salvation of soul; health, so that one can assist those in need and undertake work worthy of God; sickness, so that one may earn the crown of patience; spiritual knowledge and strength, so that one may acquire virtue; weakness and ignorance, so that, turning one's back on worldly things, one may be under obedience in stillness and humility; unsought loss of goods and possessions, so that one may deliberately seek to be saved and may be helped when incapable of shedding all one's possessions or even of giving alms; ease and prosperity, so that one may voluntarily struggle and suffer to attain the virtues and thus become dispassionate and fit to save other souls; trials and hardship so that those who cannot eradicate their own will may be saved in spite of themselves, and those capable of joyful endurance may attain perfection.
This reversal of thoughts is the strongest means, not only for repelling accidental critical thoughts, but also for completely freeing yourself of this vice…
A man is neither saved nor lost by the place he is in, but is saved or lost by his deeds. Neither a holy place nor a holy state is of use to him who does not fulfill the commandments of the Lord.
For God seeks nothing else from us, save a good purpose. Say not, How are my sins blotted out? I tell thee, By willing, by believing. What can be shorter than this? But if, while thy lips declare thee willing, thy heart be silent, He knoweth the heart, who judgeth thee. Cease from this day from every evil deed. Let not thy tongue speak unseemly words, let thine eye abstain from sin, and from roving after things unprofitable.
At this point the zealous man looks inward, and what do you think he finds there? Ceaseless wandering of thoughts, constant onslaughts from the passions, hardness and coldness of heart, obstinacy and disobedience, desire to do everything according to his own will. In a word, he finds everything within himself in a very bad state. And seeing this, his zeal is inflamed, and he now directs strenuous efforts to the development of his inner life, to controlling his thoughts and the dispositions of his heart. From directions on inner spiritual life he discovers the necessity of paying attention to oneself, of watching over the movements of the heart. In order not to admit to anything bad, it is necessary to preserve the remembrance of God. And so he sets to work to achieve this remembrance. But his thoughts can no more be arrested than the wind; his bad feelings and worthless impulses can no more be evaded than the stench of a corpse; his mind, like a wet and frozen bird, cannot rise to the remembrance of God. What is to be done? Be patient, they say, and go on working. Patience and labor are exercised, but all within remains the same. At last someone of experience is found who explains that all is inwardly in disorder because the forces within are divided: mind and heart each go their own way. Mind and heart must be united; then wandering of thoughts will cease, and you will gain a rudder to steer the ship of your soul, a lever by which to set in movement all your inner world. But how can one unite mind and heart? Acquire the habit of praying these words with the mind in the heart, 'Lord Jesus Christ, Son of God, have mercy upon me'. And this prayer, when you learn to perform it properly, or rather when it becomes grafted to the heart, will lead you to the end which you desire. It will unite your mind with your heart, it will cut off your wandering thoughts, and give you the power to govern the movements of your soul.
If however any one thinks that he is not being burned when sinning, to him the Scripture saith, Shall a man wrap up fire in his bosom, and not burn his clothes? For sin burns the sinews of the soul, and breaks the spiritual bones of the mind, and darkens the light of the heart.
Guard thyself then, O man; thou hast the signs of Antichrist; and remember them not only thyself, but impart them also freely to all. If thou hast a child according to the flesh, admonish him of this now; if thou hast begotten one through catechizing, put him also on his guard, lest he receive the false one as the True. For the mystery of iniquity doth already work. I fear these wars of the nations; I fear the schisms of the Churches; I fear the mutual hatred of the brethren. But enough on this subject; only God forbid that it should be fulfilled in our days; nevertheless, let us be on our guard. And thus much concerning Antichrist.