1. Though the consciences of such men are awakened, yet their minds are not changed: therefore, when the power of guilt weareth away, that which provoked them to be religious ceaseth; wherefore they naturally turn to their own course again; even as we see the dog that is sick of what he hath eaten, so long as his sickness prevails, he vomits and casts up all; not that he doth this of a free mind, (if we may say a dog has a mind,) but because it troubleth his stomach: but now, when his sickness is over, and so his stomach eased, his desires being not at all alienated from his vomit, he turns him about, and licks up all; and so it is true which is written, “The dog is turned to his own vomit again.” 2 Pet. 2:22. Thus, I say, being hot for heaven, by virtue only of the sense and fear of the torments of hell, as their sense and fear of damnation chills and cools, so their desires for heaven and salvation cool also. So then it comes to pass, that when their guilt and fear is gone, their desires for heaven and happiness die, and they return to their course again.
2. Another reason is, they have slavish fears that do overmaster them: I speak now of the fears that they have of men; “For the fear of man bringeth a snare.” Prov. 29:25. So then, though they seem to be hot for heaven so long as the flames of hell are about their ears, yet, when that terror is a little over, they betake themselves to second thoughts, namely, that it is good to be wise and not to run (for they know not what) the hazard of losing all, or at least of bringing themselves into unavoidable and unnecessary troubles; and so they fall in with the world again.
3. The shame that attends religion lies also as a block in their way: they are proud and haughty, and religion in their eye is low and contemptible: therefore when they have lost their sense of hell and the wrath to come, they return again to their former course.
4. Guilt, and to meditate terror, are grievous to them; they like not to see their misery before they come into it; though perhaps the sight of at it first, if they loved that sight, might make them fly whither the righteous fly and are safe; but because they do, as I hinted before, even shun the thoughts of guilt and terror, therefore, when once they are rid of their awakenings about the terrors and wrath of God, they harden their hearts gladly, and choose such ways as will harden them more and more.
To Sum it up in our own words:
1) When the fear of damnation subsides he returns to the SINS which he formerly enjoyed. Take note of the grotesque detail of Bunyan describing the DOG returning to his own VOMIT.
2) When it is fear of MEN that causes you to run for Heaven that to will pass and you will turn back.
3) Shame that attends religion. Never be ashamed. You will and may be tempted by family, friends, workers, and employers to avoid their censorious looks, thoughts and opinions. But Temporary because of this Shame turns back.
4) Guilt and Terror are not pleasant thoughts. Why think of Hell before you come to it? If you can silence this then you can once again return to the vomit - to harden more and more your own heart.