Good essay from Timothy Flanders at 1P5. Here is a preview. -nvp
During Lent, it is easy to focus a great deal on fulfilling your resolutions, but what is the purpose of these resolutions? If we lose sight of their proper end, we risk wasting our time and effort in the spiritual life. This article will discuss the aim we must have for the Great Fast of Lent, in order that our efforts may not be in vain but produce the necessary fruit in the spiritual life.
Growth in Charity
The aim of the spiritual life, and thus the goal of Lent, is growth in charity. Garrigou-Lagrange writes:
Christ incessantly reminds us that the supreme precept dominating all others and all the counsels is the precept of love[.] … Charity is the bond of perfection because it is the highest of the virtues which unites our soul to God. It ought to last forever, and it vivifies all the other virtues by rendering their acts meritorious, ordaining them to the last end, that is, to its object: God loved above all else. 
Thus the chief aim of all our Lenten practices must be the growth in charity. If we spend our time in Lent in everything else but this, our whole time will have been wasted. This why on the Sunday before Ash Wednesday the Church proclaims these sublime verses from the Apostle:
If I speak with the tongues of men, and of angels, and have not charity, I am become as sounding brass, or a tinkling cymbal. And if I should have prophecy and should know all mysteries, and all knowledge, and if I should have all faith, so that I could remove mountains, and have not charity, I am nothing. And if I should distribute all my goods to feed the poor, and if I should deliver my body to be burned, and have not charity, it profiteth me nothing (I Cor. 13:1–3).
In other words, if you fast perfectly throughout Lent and pray for hours, wearing a hair shirt, sitting in ashes all day long, but do not grow in charity, you have wasted your time. What is worse, you may have acquired the pride of demons instead of the humility of saints. We must keep this aim in mind for all our practices for Lent.
The Chief Enemy of Charity: The Predominant Fault
The supernatural virtue of charity (with the other virtues) is given in holy baptism. Mortal sin destroys charity in the soul, but absolution restores charity with the other virtues. So if we truly have these virtues, why are we not virtuous?
The virtues present within a soul in a state of grace are blocked by the effects of Original Sin. Therefore, the more the pious soul overcomes these effects by the power of grace, the more the virtues can show their effects. Above all, the predominant fault is the thing that prevents growth in charity and the other virtues. In a previous article, we mentioned the predominant fault as one of the three pillars in the spiritual life. Garrigou-Lagrange defines it this way:
The predominant fault is the 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[.] … The predominant fault is so much the more dangerous as it often compromises our principle good point, which is a happy inclination of our nature that ought to develop and to be increased by grace[.] … 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. 
Thus, in order to grow in charity, we must focus on our predominant fault. This is the weak point keeping us from advancing in the spiritual life. In confession, we may feel overwhelmed with all of our sins and faults and think we need to focus on all our habitual sins at once. But this is a trick of the Devil, who seeks to turn you to despair if you do not advance on every front of the spiritual life at the same time.
Thankfully, we need not focus on every sin at the same time, but above all on our predominant fault. This is why the spiritual writers identify the predominant fault as one of the three pillars of the spiritual life, together with prayer and spiritual reading. If we focus on this, our other sins will also be overcome…
(this is Mark again. There is much more at the link, including an excellent treatment on the Four Temperments. Knowing which of the four you are goes a long way toward rooting out your Predominant Fault)