One who comprehends that at the root of indifference (a dangerous behavioral disorder) lies weakness of faith should immediately resort to the methods instructed in the Qur'an to cure himself of this disease. First of all, he must be aware that the main source of energy is consciousness of Allah and put forth efforts to achieve it. Through deep contemplation he must strive to attain a deep faith. He must pray to Allah and ask His help while not hesitating to undertake anything that will improve him.
No doubt, in such a situation one needs to use reason. In the Qur'an, Allah shows that employing one's intellect is the way that guides man to the right path. A person must think about the existence and greatness of Allah, His mercy to mankind, and then comprehend the importance of earning His approval. Similarly, he must think about the purpose of his creation and the way that Allah tests him. He must know that Allah is with him and constantly sees and hears him. He should keep in mind that everything he does, whether important or insignificant, is known by Allah and that he will have to give an account of his deeds on the Day of Judgement.
He must also remember that death is very near and that it may come upon him abruptly. Moreover, he must grasp the fact that the life of this world is brief and that engaging in good deeds to be worthy of Paradise is extremely urgent.
He should reflect on the beauty of Paradise and the great pleasure of its blessings, and try to understand the concept of eternity. He should realize that Hell is a place created only to give anguish to the human body and soul; nothing good, joyful or pleasing exists there, and its inhabitants will remain for all eternity. He must be aware that he will feel overwhelming regret during every moment of his eternal existence unless he now gives serious consideration to the warnings.
If a man ponders sincerely, he will surely arrive at the right conclusion. He will see that rather than meeting such an end, to follow his conscience and hold fast to the religion eagerly is much less difficult. Thus, he will make the right decision and devote the rest of his life - not much more than a couple of decades anyway - to earning the acceptance of Allah, His love and His mercy, and will do his best to win the Paradise Allah promises.
Contemplating the possibility of being in Hell even for a moment causes one to alter his conduct because Hell is such a place that no regret in this world is comparable to the regret felt there. Similarly, no pain in this world can be more intense than the pain in Hell. Reading the verses related to Hell to gain a full understanding of it, as something to be avoided is an effective way of becoming more enthusiastic.
Everyone should think about these facts and realize that lack of enthusiam is the result of a distorted outlook on the world and the Hereafter and then begin engaging in good deeds as soon as possible. He must remember that the indifference he shows in the face of happenings around him may cause him, in time, to lose his sensitivity of conscience and heart entirely. Therefore, he must hasten to avoid such a condition:
"Has the time not come for those who have believed that their hearts should become humbly submissive at the remembrance of Allah and what has come down of the truth? And let them not be like those who were given the Scripture before, and a long period passed over them, so their hearts hardened; and many of them are defiantly disobedient." (Surat al-Hadid, 16)
In another verse also Allah warns about the hardening of hearts:
"Then your hearts became hardened after that, being like stones or even harder. For indeed, there are stones from which rivers burst forth, and there are some of them that split open and water comes out, and there are some of them that fall down for fear of Allah. And Allah is not unaware of what you do." (Surat Al-Baqara, 74)
In the above verse Allah has given an example of stones from which water emerges and others that crash down from fear of Him. Fear of Allah, as this example reveals, will render unenthusiastic people zealous and lead them to adopt the good values enabling them to compete in righteousness for the sake of Allah.