Nicene and Post-Nicene Fathers, Ser. II, Vol. XI:
The Works of John Cassian.: Chapter VIII. Of the practices in which the juniors are first exercised that they may become proficient in overcoming all their desires.

Chapter VIII.

Of the practices in which the juniors are first exercised that they may become proficient in overcoming all their desires.

And his anxiety and the chief part of his instruction—through which the juniors brought to him may be able in due course to mount to the greatest heights of perfection—will be to teach him first to conquer his own wishes; and, anxiously and diligently practising him in this, he will of set purpose contrive to give him such orders as he knows to be contrary to his liking; for, taught by many examples, they say that a monk, and especially the younger ones, cannot bridle the desire of his concupiscence unless he has first learnt by obedience to mortify his wishes. And so they lay it down that the man who has not first learnt to overcome his desires cannot possibly stamp out anger or sulkiness, or the spirit of fornication; nor can he preserve true humility of heart, or lasting unity with the brethren, or a stable and continuous concord; nor remain for any length of time in the monastery.