Nicene and Post-Nicene Fathers, Ser. II, Vol. XI:
The Works of John Cassian.: Chapter III. How pride is equally destructive of all virtues.

Chapter III.

How pride is equally destructive of all virtues.

There is then no other fault which is so destructive of all virtues, and robs and despoils a man of all righteousness and holiness, as this evil of pride, which like some pestilential disease attacks the whole man, and, not content to damage one part or one limb only, injures the entire body by its deadly influence, and endeavours to cast down by a most fatal fall, and destroy those who were already at the top of the tree of the virtues. For every other fault is satisfied within its own bounds and limits, and though it clouds other virtues as well, yet it is in the main directed against one only, and specially attacks and assaults that. And so (to make my meaning clearer) gluttony, i.e., the appetites of the belly and the pleasures of the palate, is destructive of strict temperance: lust stains purity, anger destroys patience: so that sometimes a man who is in bondage to some one sin is not altogether wanting in other virtues: but being simply deprived of that one virtue which in the struggle yields to the vice which is its rival and opposed to it, can to some extent preserve his other virtues: but this one when once it has taken possession of some unfortunate soul, like some most brutal tyrant, when the lofty citadel of the virtues has been taken, utterly destroys and lays waste the whole city; and levelling with the ground of vices the once high walls of saintliness, and confusing them together, it allows no shadow of freedom henceforth to survive in the soul subject to it. And in proportion as it was originally the richer, so now will the yoke of servitude be the severer, through which by its cruel ravages it will strip the soul it has subdued of all its powers of virtue.