Our last contest is against the spirit of pride. Albeit it is the last disease we have to fight and the closing member of the list, yet in time and origin it is first of all. It is a beast most savage, and fiercer than all the others: its worst temptations attack the perfect, and it devours with its most deadly bite those who have all but reached the crown and sum of all virtues.
Of this disease there are two kinds: one, which attacks the spiritual and the most advanced, and another, that throws its toils over even beginners and the carnal minded. And, although either kind of pride is induced by an evil spirit of arrogance, as well towards God as towards man, yet the first kind has specially to to with God, and the second is more properly referred to our fellow men.
There is no other vice which in this sort renders all the virtues of none effect, and so strips a man of every kind of justice and holiness as this disease of pride….it corrupts the whole man….gluttony corrupts the integrity of temperance, lust defiles chastity, anger ravages the virtue of patience…but this vice, when it has got a hold on the unhappy mind of its victim, like some wild and raging tyrant captures the topmost citadel of the virtues, and brings them to dust, and utterly lays low the whole edifice….it permits henceforth no single sign of liberty to remain in the soul that it has subdued.
~St John Cassian
Prayerful Life 