The wise Solomon says in the Proverbs, "They that have no guidance fall like leaves; but in much counsel there is safety." So you see what the Holy Scriptures teach us? They enjoin us not to rely on ourselves, not to regard ourselves as knowing all, not to believe that we can control ourselves, for we need help, and are in need of those who would counsel us according to God. No men are more unfortunate or nearer perdition than those who have no teachers on the way of God. For what does it mean that where no guidance is, the people fall like leaves? A leaf is at first green, flourishing, beautiful., then it gradually withers, falls, and is finally trampled underfoot. So it is with a man who has no guide: at first he is always zealous in fasting, vigil, silence, obedience, and other virtues; then his zeal, little by little, cools down and, having no one to instruct, support, and fire him up with zeal, he insensibly withers, falls, and finally becomes a slave of the enemies, who do with him what they will.

(The Philokalia)