What is meant by the Predominant Fault? The noted theologian Reginald Garrigou – Lagrange explains,

“The predominant fault is that defect in us that tends to prevail over the others, and thereby over our manner of feeling, judging, sympathizing, willing, and acting. It is a defect that has in each of us an intimate relation to our individual temperament. 
 
Evidently it is of primary importance that we recognize our predominant fault and have no illusions about it. This is so much the more necessary as our adversary, the enemy of our soul, knows it quite well and makes use of it to stir up trouble in and about us. In the citadel of our interior life, which is defended by the different virtues, the predominant fault is the weak spot, undefended by the theological and moral virtues. The enemy of souls seeks exactly this easily vulnerable point in each one, and he finds it without difficulty. Therefore, we must recognize it also.

But how can we discern it? For beginners who are sincere, this is quite easy. But later the predominant fault is less apparent, for it tries to hide itself and to put on the appearances of a virtue: pride clothes itself in the outward appearances of magnanimity, and pusillanimity seeks to cover itself With those of humility. Yet we must succeed in discerning the predominant fault, for if we do not know it, we cannot fight it; and if we do not fight it, we have no true interior life.

That we may discern it, we must first of all ask God for light: “Lord, make me know the obstacles I more or less consciously place in the way of the working of Thy grace in me. Then give me the strength to rid myself of them, and, if I am negligent in doing so, do please free me from them, though I should suffer greatly.”

After thus asking sincerely for light, we must make a serious examination. How? By asking ourselves: “Toward what do my most ordinary preoccupations tend, in the morning when I awake, or when I am alone? Where do my thoughts and desires go spontaneously?”

We should keep in mind that the predominant fault, which easily commands all our passions, takes on the appearance of a virtue and, if it is not opposed, it may lead to impenitence. Judas fell into impenitence through avarice, which he did not will to dominate; it led him to impenitence like a violent wind that hurls a ship on the rocks.

— from The Three Ages of the Spiritual Life

He was chosen. One of the Twelve. So, who can afford to be be so preoccupied in worldly, intellectual or even ecclesiastical matters that we forget our own souls?