Those who are regretful in the Hereafter because they didn't use their reason as they were supposed to in this world are mentioned by the Quran as saying:
"If only we had really listened and understood, we would not now have been the heirs of Hell." (Surat al-Mulk: 10)
Without a doubt, if a person thinks that such a consequence is also possible in his own case, it will enable him to be fearful and apprehend many things while there is still time. If a person in this situation ends up in Hell, he will most likely think with regret that even although his conscience had made him see things clearly in the world, possibly after numerous reminders, and despite there being no obstacles in his path, he still turned away from the way of intelligence.
However, by that time he is in Hellfire, where it is impossible for him to go back and compensate for his situation…
When he was in the world, he was reminded of Allah's punishment, but he didn't listen to these warnings because of his arrogance…
By saying "In any case there is a long life ahead of me, I can compensate for it in the future", he always delayed doing the right thing…
The wealth, beauty, or knowledge he possessed in the world gave him a feeling of greatness and prevented him from obeying Allah…
But at that moment there is nothing he can do to save himself from the fire and punishment; he is in a state of helplessness…
And whatever he does now, he can never get rid of the regret that he feels deep inside and he will constantly complain about his own thoughtlessness…
So, for a person to think, while he is still in this world, that he may face such a situation will result in his feeling deep regret there and then. In order not to say these words or words like these in Hellfire, he will decide to abide by his conscience from then on. When he consults his conscience, he will come across little and big things that everyone delays, or disregards, thinking them insignificant, or doesn't do, even if they know they are the right things to do. and it is possible for everyone to compensate for all these things right now.
If you ask anyone "Is it wiser to do this soul searching when full of regret in Hellfire, or now when there is still a chance to make up for it?" any sincere person would definitely say, "Of course now, in fact, right this second." Then he will turn his mind to trying to make up for all the unjust things he has done so far, without further delay.
In fact, this is the wisest action to take. Imagining oneself in the midst of Hellfire, even for a second, is enough for anyone to reach this sincere decision and act by his conscience. It is really easy for a person who trusts in and relies on Allah to make up for all his thoughtless and unjust behaviour till that moment. In the following verse, Allah informs people of the simplicity of this:
Say: "My servants, you who have transgressed against yourselves, do not despair of the mercy of Allah. Truly Allah forgives all wrong actions. He is the Ever-Forgiving, the Most Merciful". (Surat az-Zumar: 53)
However, a person should make haste in these matters and not wait for hardship or death before he uses his reason. Allah reminds people in this verse that they need to act without wasting any time:
Turn to your Lord and submit to Him before punishment comes upon you, for then you cannot be helped. Follow the best that has been sent down to you from your Lord before the punishment comes upon you suddenly, when you are not expecting it. (Surat az-Zumar: 54-55)
It shouldn't be forgotten that one who sees the truth by consulting his conscience can make amends for the situation he is in. But, anyone who insists on not using his reason will definitely face the divine ire, having been led into regrettable acts that cannot be compensated for. In the following verse, the regret such people voice in the Hellfire is thus alluded to:
"... Alas: I have disobeyed Allah, and scoffed at His revelations!" (Surat az-Zumar: 56)
So this was what was intended in this book—to encourage people to do whatever they can right now in order not to face such a loss. With this purpose in mind, wisdom and thoughtlessness have been compared right from the beginning of the book and readers have been informed of the relative gains and losses. and at the end of the book it has been recalled once more, that thoughtlessness distances people from faith and, because of this, leads them into the torments of Hell. On the other hand, wisdom brings people to the blessings of Heaven. In order not to live with the guilt of thoughtlessness and a lack of conscience, everyone is invited once more to use his reason and find the right path.