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.
Grow calm, grow quiet after harmful noise... you will experience a certain movement towards eternity; gradually, like a still, small voice, a thought will come to you as to who you are and what is your end and purpose... this is a sign of the approach of the word of God in your soul.
Try to know yourself, your own wickedness. Think on the greatness of God and your wretchedness. Meditate on the suffering of Christ, the magnitude of Whose love and suffering surpass our understanding. Ascribe the good that you do to God alone. Do not think about the sin of a brother but about what in him is better than in yourself.... Flee from glory, honors and praise, but if this is impossible, be sorry that such is your lot. Be benevolent to people of low origin. Be freely and willingly obedient not only to those above you but to those below .... The lowlier we are in spirit, the better we know ourselves, and without humility we cannot see God.
Grace is the food and clothing of the saints. It wakens grief in a man's heart, making him dissatisfied and moving him to seek the reason of this dissatisfaction. Grace gives sorrow and grace comforts; showing us the poverty of all things, it engenders in us a repentant sorrow for having fallen short of the love of God... One who is possessed by such sorrow will always grieve, for he thinks of God's offended love and not of the fear of hell. It is a grief of love.
Do not neglect the practice of the virtues; if you do, your spiritual knowledge will decrease, and when famine occurs you will go down into Egypt (Genesis 41:57, 46:6).