Here is Garrigou-Lagrange on this point.
He enlightens them through the gifts of wisdom and understanding, knowledge and counsel, which with sanctifying grace and charity we received in baptism and to a greater degree in confirmation. In imperfect souls these gifts, together with those of piety, fortitude, and filial fear, are, so to speak, shackled by more or less inordinate inclinations, so that such souls are living but a superficial life, which prevents them from being attentive to the inspirations of the Master of the interior life.
These gifts have been likened to the sails of a boat by which it readily accommodates itself to the least stir of a favorable wind. In imperfect souls, however, the sails are furled and will not respond to the breeze. On the other hand, when the soul does what it can to fulfil its daily obligations and steer its bark as it should, abandoning itself to God, He visits it with His inspirations, at first latent and confused, which if well received, become more and more frequent, more insistent and luminous.
Then, amidst the joyful and painful events of life, the clash of temperaments, in times of spiritual dryness, amidst the snares of the devil or of men, their suspicion and their jealousies, the soul in its higher regions at any rate remains always at peace. It enjoys this serenity because it is intimately persuaded that God is guiding it and, in abandoning itself to Him, it seeks only to do His will and nothing more. Thus it sees Him everywhere under every external guise and makes use of everything to further its union with Him. Sin itself, by its very contrast, will recall the infinite majesty of God.
Then is increasingly realized the words of the Apostle St. John to the faithful for whom he wrote his First Epistle: "Let the unction you have received from God abide in you. And you have no need that any man teach you: but as His unction teacheth you of all things, and is truth, and is no lie" (I John 2:27).