Pride is regarded as the most dangerous passion by the Desert Fathers and tne Eastern Orthodox monks, as documented in works such as The Ladder of Divine Ascent, the Philokalia, an anthology on monasticism, mystical theology, prayer and hesychasm, and the Arena, a guidebook for monastics by the 19th century Russian Orthodox bishop (who like most Orthodox bishops, began as a monk, and remained a member of the monastery throughout his career). Indeed, we see the devil attempting to appeal to pride on the part of our Lord, in vain, for God is sinless, and likewise attempting to trip up St. Anthony the Great, the first widely known Desert Father, in the excellent biography of him by St. Athanasius.
Basically, the danger is that as monks conquer the other passions, like lust, gluttony, sloth, avarice and so on, they are at risk of pride, and can become deluded that they accomplished this spiritual feat, when in fact it was the result of the Holy Spirit working within them synergistically.
Consequently, this is immediately relevant to us, living in the world, and not just to monasteries, because if we advance in our Christian faith in some way, by learning to resist a persistent temptation, we can be tempted by pride to ignore that our progress was enabled by the infinite and uncreated grace freely given by God the Holy Spirit, and the most we did was cooperate with that grace, and so, believing ourselves to have advanced on our own, in a kind of Pelagian conceit, we undo whatever progress we had made through the grace and loving kindness of our Lord and Paraclete, the Holy Spirit, sent by our savior to help us follow Him.
