Milton does a masterful job of portraying Satan's guilt in Book IV of Paradise Lost. At this point in the poem, Satan has escaped hell, and has just taken his first look into the created world, but he has no sense of joy. Milton shows great psychological insight into the effects of sin and guilt. This is a moment when Satan should be glad, but instead,

     . . . Horror and doubt distract
     His troubled thoughts, and from the bottom stir
     The hell within him; for within him Hell
     He brings, and round about him, nor from Hell
     One step, no more than from Himself, can fly
     By change of place. Now conscience wakes despair
     That slumbered; wakes the bitter memory
     Of what he was, what is, and what must be
     Worse; of worse deeds worse sufferings must ensue.

Lines 19-26

Some Christians take the path of stoicism in the fight against sensuality. It doesn't work. It's not biblical. It is hopelessly weak and ineffective. And the reason it fails is that the power of sin comes from its promise of pleasure and is meant to be defeated by the ... promise of superior pleasure in God, not by raw human willpower. Willpower religion, when it succeeds, gets glory for the will. It produces legalists, not lovers.

John Piper, When I Don't Desire God: How to Fight for Joy, p. 103

In A Preface to Paradise Lost, C. S. Lewis discusses Book IX, lines 811 ff., of Paradise Lost, in which Eve has just eaten the fruit, and is now planning to give it to Adam. She reasons that if she is going to die, she must have Adam die with her. As Lewis points out, Eve is planning to actually murder Adam, but the reader may not even notice this, because the shift in her thinking is so subtle. Lewis then makes an insightful comment about human nature:

If the precise movement of Eve's mind at this point is not always noticed, that is because Milton's truth to nature is here almost too great, and the reader is involved in the same illusion as Eve herself. The whole thing is so quick, each new element of folly, malice, and corruption enters so unobtrusively, so naturally, that it is hard to realize we have been watching the genesis of murder. We expect something more like Lady Macbeth's 'unsex me here'. But Lady Macbeth speaks thus after the intention of murder has already been fully formed in her mind. Milton is going closer to the actual moment of decision. Thus, and not otherwise, does the mind turn to embrace evil. No man, perhaps, ever at first described to himself the act he was about to do as Murder, or Adultery, or Fraud, or Treachery, or Perversion; and when he hears it so described by other men he is (in a way) sincerely shocked and surprised. Those others 'don't understand'. If they knew what it had really been like for him, they would not use those crude 'stock' names. With a wink or a titter, or in a cloud of muddy emotion, the thing has slipped into his will as something not very extraordinary, something of which, rightly understood and in all his highly peculiar circumstances, he may even feel proud. If you or I, reader, ever commit a great crime, be sure we shall feel very much more like Eve than Iago.

It is not enough to watch our circumstances to detect the times of temptation. We must also watch our heart to know when temptation might approach us.

We need to know our own heart, our natural disposition, and the lusts, corruptions, and spiritual weaknesses that beset us. . . . David tells us he considered his ways and kept himself from the iniquity to which he was prone (Psalm 18:23).

Just as people have differing and distinctive personalities, so they are also affected by distinctive temptations. These relate to their nature, education, and other factors. Unless we are conscious of these propensities, relationships, and dynamic possibilities, temptation will constantly entangle us. This is why it is so important to know ourselves.

John Owen, Sin and Temptation

From Augustine's Confessions, Book 2:

The life which we live in this world has its attractiveness because of a certain measure in its beauty and its harmony with ... objects that are beautiful. Human friendship is also [a source of happiness]. Yet sin is committed for the sake of all these things ... when, in consequence of an immoderate urge towards those things which are at the bottom of the scale of good, we abandon the higher and supreme goods, that is you, Lord God, and your truth and your law (Ps. 118: 142). These inferior goods have their delights, but not comparable to my God, who has made them all.

From Jonathan Edwards' "Advice to Young Converts":

Be always greatly humbled by your remaining sin, and never think that you lie low enough for it, but yet don't be at all discouraged or disheartened by it. Although we are exceedingly sinful, we have an advocate with the Father, Jesus Christ the righteous, the preciousness of whose blood, the merit of whose righteousness, and the greatness of whose love and faithfulness infinitely overtop the highest mountains of our sins.