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.
Labor to acquire meekness. Concerning the heavenly virtues, meekness and humility, the Lord Himself teaches us, saying: Learn of Me, for I am meek and humble in heart; and ye shall find rest unto your souls (Matt. 11:29). Learn not from angels, nor from men, but from Me, He says; that is, from the higher wisdom.
I suppose that it is sometimes better to fall oneself and rise, than to judge one's neighbor; because one who has sinned is incited to self-abasement and repentance, while he who judges one who has sinned becomes hardened in an illusion about himself and in pride. Therefore everyone must guard himself, as much as possible, so as not to judge.
Those who have truly decided to serve the Lord God should practice the remembrance of God and uninterrupted prayer to Jesus Christ, mentally saying: Lord Jesus Christ, Son of God, have mercy on me, a sinner.
Therefore with your whole soul you should acknowledge yourself as worthy of enduring more than you already endure; remember the words which Christ the Savior spoke concerning a good deed done to one’s neighbor, words which should apply equally to every offensive word or deed against one’s neighbor. Whatever you have done to your neighbor, He says, you have done to Me.
He who knows himself pays no heed to the sins of others, but looks at his own and is always repenting over them; he reflects concerning himself, and condemns himself, and does not interfere in anything apart from his own position.
Fasting needn't be limited to abstinence from food alone, because true fasting is departure from evil deeds. Forgive your neighbor any insult, abstain from causing your neighbor offence, abstain from irritation, from senseless sorrows, from fear, wrath, and so on. ‘True fasting is alienation from evil, temperance of the tongue, setting aside of wrath, casting out of lust, idle talk, lies, and oath-breaking’…This is a true and pleasing fast for the Lord. Departing from these vices and from a corrupt state is what comprises a true fast.
First of all it must be understood that it is the duty of all Christians - especially of those whose calling dedicates them to the spiritual life - to strive always and in every way to be united with God, their creator, lover, benefactor, and their supreme good, by whom and for whom they were created. This is because the center and the final purpose of the soul, which God created, must be God Himself alone, and nothing else - God from whom the soul has received its life and its nature, and for whom it must eternally live. For all visible things on earth which are lovable and desirable - riches, glory, wife, children, in a word everything of this world that is beautiful, sweet, and attractive - belong not to the soul but only to the body, and being temporary, will pass away as quickly as a shadow. But the soul, being eternal by its nature, can attain eternal than all beauty, sweetness, and loveliness, and He is its natural home, whence it came and whither it must return. For as the flesh coming from the earth returns to the earth, so the soul coming from God returns to God and dwells in Him. For the soul was created by God in order to dwell in Him forever; therefore in this temporary life we must diligently seek union with God, in order to be accounted worthy to be with Him and in Him eternally in the future life.