Unbelievers cannot be happy because they do not look for solutions in the Qur'an

Not looking for answers in the Qur'an is one of the first errors made in a society of ignorance. They see clearly that the situation in which they find themselves is a dead end. They recognize that the lifestyle they have adopted and the character they have assumed have not led them anywhere; that these things have been unsatisfying and even disappointing. In response, they experiment with other alternatives provided by the society of ignorance, but find that these too bring them nothing. Because, one ignorant pattern of behavior is basically no different than another. People, places and conditions may change, but the false expectations and anxiety remain the same; the "intellectual" and the "socialite" are both focused on this world.

However, this earthly life is too brief to be worth becoming overly attached to. There is nothing to be gained from this world; when a person dies, everything he had will be taken from him. For this reason, every kind of undue devotion to this world gives rise only to anxiety.

But, the solution has already been provided; a human being can find happiness only when he turns to Allah. A person can be saved from his troubles only by being Allah's friend and leading the kind of life He wills.

In the Qur'an, Allah reveals this important secret:

Those who believe and whose hearts find peace in the remembrance of Allah. Only in the remembrance of Allah can the heart find peace. (Surat ar-Ra'd, 28)

One who had become the friend of Allah strictly obeys the Book sent down by our Lord to guide him.

From that point on, his personality and lifestyle are determined only by the Qur'an. Therefore, by the will of Allah, the Qur'an can lead human beings from darkness to light:

Alif Lam Ra. This is a Book We have sent down to you so that you can bring humanity from the darkness to the light, by the permission of their Lord, to the Path of the Almighty, the Praiseworthy. (Surah Ibrahim, 1)

For this reason, there is no anxiety, discontent, worry or confusion in the personality derived from the teachings of the Qur'an. Instead, there is beauty, balance and faultless manners. Allah has promised such believers that He will offer them the finest reward for the good they do.

So that Allah can reward them for the best of what they did and give them more from His unbounded favor. Allah provides for anyone He wills without reckoning. (Surat an-Nur, 38)