This is from the same book, A Study of Conscience, From Scripture and Documents of Vatican II, by Sister Immaculata (p.34)
The Characteristics of a Bad Conscience
Conscience frequently errs from invincible ignorance without losing its dignity. The same cannot be said of a man who cares but little for truth and goodness, or of a conscience which by degrees grows practically sightless as a result of habitual sin.
There is possible an actual resultant hatred of truth because the will will not accept it. Though the light has come into the world men have shown they prefer darkness to the light because their deeds were evil (John 3:19) Those who do evil become more and more ignorant; this does not mean that the mind is incapable of learning. One may be a genius in science or art. etc., but ignorant of the way of salvation through his own fault.
B. Irrational fears plague the bad conscience. Any least refusal of truth produces bad effects in the uneasiness, inner disharmony and disunity of the soul; the sweet control of reason is lost. Feelings of sadness, discouragement, weakening of motivation begin to take hold on us; we no longer even "see" the reasons for the most perfect actions. Our former ideals of virtue seem to have been impossible illusions.
The Book of Wisdom, Chapter 17, is a picture of the terrifying fears that beset the evil conscience when the power of reason, which is able to dispel fear, has been darkened and enlarged by the contradiction of sin; it is no longer able to exert its own strength to control the emotions. The passage speaks of the Egyptian darkness (NB: Didn't want to type Sister's translation, so copied this from the online NAB, varies slightly from what is in her book).
For when the lawless thought to enslave the holy nation, shackled with darkness, fettered by the long night, they lay confined beneath their own roofs as exiles from the eternal providence. For they who supposed their secret sins were hid under the dark veil of oblivion were scattered in fearful trembling, terrified by apparitions. For not even their inner chambers kept them fearless, for crashing sounds on all sides terrified them, and mute phantoms with somber looks appeared. No force, even of fire, was able to give light, nor did the flaming brilliance of the stars succeed in lighting up that gloomy night. But only intermittent, fearful fires flashed through upon them; and in their terror they thought beholding these was worse than the times when that sight was no longer to be seen. And mockeries of the magic art were in readiness, and a jeering reproof of their vaunted shrewdness. For they who undertook to banish fears and terrors from the sick soul themselves sickened with a ridiculous fear. For even though no monstrous thing frightened them, they shook at the passing of insects and the hissing of reptiles, and perished trembling, reluctant to face even the air that they could nowhere escape. For wickedness, of its nature cowardly, testifies in its own condemnation, and because of a distressed conscience, always magnifies misfortunes. For fear is nought but the surrender of the helps that come from reason; and the more one's expectation is of itself uncertain, the more one makes of not knowing the cause that brings on torment. So they, during that night, powerless though it was, that had come upon them from the recesses of a powerless nether world, while all sleeping the same sleep, were partly smitten by fearsome apparitions and partly stricken by their souls' surrender; for fear came upon them, sudden and unexpected. Thus, then, whoever was there fell into that unbarred prison and was kept confined. For whether one was a farmer, or a shepherd, or a worker at tasks in the wasteland, Taken unawares, he served out the inescapable sentence; for all were bound by the one bond of darkness. And were it only the whistling wind, or the melodious song of birds in the spreading branches, or the steady sound of rushing water, or the rude crash of overthrown rocks, or the unseen gallop of bounding animals, or the roaring cry of the fiercest beasts, or an echo resounding from the hollow of the hills, these sounds, inspiring terror, paralyzed them. For the whole world shone with brilliant light and continued its works without interruption; over them alone was spread oppressive night, an image of the darkness that next should come upon them; yet they were to themselves more burdensome than the darkness.
A guilty conscience is its own punishment and through the "hardness" of malice may not have reached the degree described in the above passage there is always some degree of fear and weakness, moral, psychological and even physical because the whole person is laboring under an unnatural strain. Psalm 38 describes the guilty man in the struggle to overcome the heavy load of sin and unconfessed guilt. Sin produces habits, ingrained in our psyche and in our body itself, which cannot easily be conquered even when we have repented and want to return to doing good.
Yahweh, do not punish me in your rage,
or reprove me in the heat of anger.
Your arrow have pierced deep,
Your hand has pressed down on me;
no soundness in my flesh now you are angry,
no health in my bones, because of my sin.
My guilt is overwhelming me;
it is too heavy a burden;
bowed down, bent double, overcome,
I go mourning all the day (v. 1-6)
C. Malice -- a "hardening" in the lie is a denial of God.
Sin is a lie in the very being and the sinner takes to lying more and more easily. Not a word of their lips can be trusted, deep within them lies ruin (Psalms 5:9) The lie, persisted in becomes the very denial of God Himself: The fool says in his heart: "there is no God" their deeds are corrupt and vile (Psalms 14:1 and 10:3-11).