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.
Prayer... by its action it is the reconciliation of man with God, the mother and daughter of tears, a bridge for crossing temptations, a wall of protection from afflictions, a crushing of conflicts, boundless activity, the spring of virtues, the source of spiritual gifts, invisible progress, food of the soul, the enlightening of the mind, an axe for despair, a demonstration of hope, the release from sorrow.
In his famous book, 'The Ladder', St John Climacus records the life of this saint. The young Acacius was a novice with an evil elder in the monastery on Sinai. The foul-tempered elder daily groused and grumbled at Acacius, and often beat him, tormenting and ill-treating him in every possible way. Acacius did not complain, but bore it all patiently and with trust that it would work for his salvation. When anyone asked him how he survived, he replied : 'Well, as before the Lord God'. After nine years of obedience and ill-treatment, Acacius died. The elder buried him and then went off to lament to another elder, a holy man, saying: 'Acacius, my disciple, is dead. 'I don't believe it' replied the holy elder , 'Acacius is not dead.' They then both went to the dead man's grave, and the holy elder called out: 'Brother Acacius, are you dead?' The obedient Acacius, obedient even in death, replied: 'I am not dead; the obedient cannot die.' Then the evil elder repented and shut himself in a cell near Acacius's grave, where he spent the rest of his life in repentance and prayer.