8 From both, then, men are in danger; both from hoping and despairing, from contrary things, from contrary affections. Who is deceived by hoping? He who says, God is good, God is merciful, let me do what I please, what I like; let me give loose reins to my lusts, let me gratify the desires of my soul. Why this? Because God is merciful, God is good, God is kind. These men are in danger by hope. And those are in danger from despair, who, having fallen into grievous sins, fancying that they can no more be pardoned upon repentance, and believing that they are without doubt doomed to damnation, do say with themselves, We are already destined to be damned, why not do what we please with the disposition of gladiators destined to the sword.
This is the reason that desperate men are dangerous: for, having no longer anything to fear, they are to be feared exceedingly. Despair kills these; hope, those. The mind is tossed to and fro between hope and despair. You have to fear lest hope slay you; and, when you hope much from mercy, lest you fall into judgment: again, you have to fear lest despair slay you, and, when you think that the grievous sins which you have committed cannot be forgiven you, you do not repent, and you incur the sentence of Wisdom, which says, “I also will laugh at your perdition.” How then does the Lord treat those who are in danger from both these maladies?
To those who are in danger from hope, He says, “Be not slow to be converted to the Lord, neither put it off from day to day; for suddenly His anger will come, and in the time of vengeance, will utterly destroy you.” To those who are in danger from despair, what does He say? “In what day soever the wicked man shall be converted, I will forget all his iniquities.” Accordingly, for the sake of those who are in danger by despair, He has offered us a refuge of pardon; and because of those who are in danger by hope, and are deluded by delays, He has made the day of death uncertain.
You know not when your last day may come. Are you ungrateful because you have today on which you may be improved? Thus therefore said He to the woman, “Neither will I condemn you;” but, being made secure concerning the past, beware of the future. “Neither will I condemn you:” I have blotted out what you have done; keep what I have commanded you, that you may find what I have promised.
Source: Tractates on the Gospel of John (New Advent)