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.
The roof of any house stands upon the foundations and the rest of the structure. The foundations themselves are laid in order to carry the roof. This is both useful and necessary, for the roof cannot stand without the foundations and the foundations are absolutely useless without the roof-- no help to any living creature. In the same way the grace of God is preserved by the practice of the commandments, and the observance of these commandments is laid down like foundations through the gift of God. The grace of the Spirit cannot remain with us without the practice of the commandments, but the practice of the commandments is of no help or advantage to us without the grace of God.
When the flesh flourishes, the soul fades; when the flesh has full liberty, the soul is straitened; when the flesh is satiated, the soul hungers; when the flesh is adorned, the soul is deformed; when the flesh overflows with laughter, the soul is surrounded by misfortune; when the flesh is in the light, the soul is in darkness...
What does it mean to be as wise as a serpent? When a serpent is attacked, it is willing to have much of its body severed, as long as it saves the head. So to be wise as a serpent means to be willing to lose everything - your wealth, your reputation, your friends - as long as you save your faith. Your faith is your head, by which you learn all truth; and by that truth your soul is set free. We should, however, recognize that the wisdom of the serpent is not enough; we must be honest and innocent as doves. Indeed it is the combination of wisdom and innocence that creates virtue. The person who is wise as a serpent can sustain the most terrible attacks and still continue to flourish as a disciple of Christ. The person who is innocent refuses to retaliate against those who make the attacks. To be as innocent as a dove means never to take revenge on those who wrong you or undermine you. Unless wisdom is tempered by innocence, one attack provokes another, and conflict continues without end. Unless innocence is tempered by wisdom, a person is so vulnerable that he will not even survive a single attack. Rest assured that no one can ever take away your faith; your wisdom guards against that. But be careful never to bear a grudge against anyone who does you wrong.
Almsgiving heals the soul's incensive power; fasting withers sensual desire; prayer purifies the intellect and prepares it for contemplation of created beings. For the Lord has given us commandments which correspond to the powers of the soul.
As a man cannot remain unscathed who spares his enemy on the field of battle, so a man engaged in spiritual warfare cannot save his soul if he spares his body.
Charity, temperance, contemplation, and prayer please God; gluttony, licentiousness, and what multiplies them, please the flesh. Therefore they who are in the flesh cannot please God. And they that are Christ’s have crucified their flesh with the passions and concupiscences.
Use your body, I beseech you, with moderation. Remember, with this body you will be raised from death when you come to be judged. Perhaps you have some doubt whether this could happen. If so, reflect in detail on what has already happened with your own self. Tell me, where were you a hundred years ago? Cannot the Creator who gave existence to a person that did not exist bring to life again to a person that did exist but is now dead? Every year He makes the corn spring to life that had withered and dies after it was sown. Do you suppose that He who raised Himself from the dead for our sake will have difficulty in raising us to new life? Or look at the trees. For a number of months they remain without fruit, even without leaves. But once the winter is past, they become green all over, new, as if risen from the dead. With better reason, and with greater ease shall we be called to new life. Do not listen to those who deny the resurrection of the body. Isaiah testifies: ‘The dead shall live again: the bodies of those who have died shall live.’ (Isa. 26:19) And according to the word of Daniel, ‘Many of those who sleep beneath the earth shall awaken, some to life eternal, the rest to eternal ruin.’ (Dan. 12:2)