For those interested in most of the postings on the predominant fault, I have tried to find most of the links on this subject, which is a Catholic idea, btw, and not a protestant one.
As one who is being dragged into looking at my predominant faults, I can assure you the journey is painful, but worth it.
As Garrigou-Lagrange notes, without a struggle, we shall not be made perfect, as we are called to be.
Mortification plays a huge part in the destruction of the predominant fault.
Let God lead into those murky waters of sin in order to deal with the predominant fault. Here is a selection from the great Dominican.
The truth is that without this persevering and efficacious struggle we cannot sincerely aspire to Christian perfection, toward which the supreme precept makes it a duty for all of us to tend. This precept is, in fact, without limit: "Thou shalt love the Lord thy God with thy whole heart and with thy whole soul and with all thy strength and with all thy mind: and thy neighbor as thyself." (11)
Without this struggle, there is no interior joy or peace, for the tranquility of order or peace comes from the spirit of sacrifice. It alone establishes us interiorly in order by putting to death all that is inordinate in US.(12)
Lastly, charity, the love of God and of souls in God, finally prevails completely over the predominant fault; it then truly occupies the first place in our soul and reigns there effectively. Mortification, which makes our principal fault disappear, delivers us and assures the predominance in our soul of our true natural qualities and of our special attraction of grace. Thus little by little, we grow to be ourselves, in the broad sense of the word, that is, to be supernaturally ourselves minus our defects. We do not have to copy in a more or less servile manner another's qualities, or enter a uniform mold that is the same for all. There is a great variety in human personalities, just as no two leaves or flowers are perfectly similar. But a person's temperament must not be crushed; it must be transformed while keeping whatever is good in it. In our temperament, our character must be the imprint of the acquired and infused virtues, especially of the theological virtues. Then, instead of instinctively referring everything to self, as is the case when the predominant fault reigns, we will turn everything back to God, think almost continually of Him, and live for Him alone; at the same time we will lead to Him those with whom we come into contact.