Satan always wishes to instill feelings of insecurity, despair over the future and a pessimistic view of events in those who adopt him as their friend. He does not want people to have faith, to be obedient to Allah, to submit to destiny or to be people who place their trust in Allah and are optimistic and filled with enthusiasm. Because these things are all characteristics that are pleasing to Allah and draw one closer to Him, and that are essential if one is to live by the moral values of the religion. Satan does not want people to draw close to Allah or to live by His religion in an enthusiastic and determined manner. For that reason, he always tries to instil feelings of weariness, pessimism and despair in people by encouraging hopelessness. 

One of the things that satan wants to make believers do, but cannot is to cause them to fall into despair in the face of seemingly unwelcome conditions. Satan has no power over sincere believers and cannot draw them to his side. Because of believers’ faith they always abide by the commandments and advice of Allah. Optimism is a commandment that Allah has definitively revealed in the Qur’an. There is therefore no question of believers behaving in any other manner on the subject. Because in His verses Allah tells believers, "... Do not despair of solace from Allah. No one despairs of solace from Allah except people who are unbelievers.” (Surah Yusuf, 87) Believers therefore strongly avoid entering any such state of mind.
Pessimism is also condemned in other verses of the Qur’an and described as a negative attribute of deniers. We are told in verses that:
 

Man never tires of praying for the good    and if evil touches him, he despairs and loses hope. But if We let him taste mercy from Us     after he has suffered hardship, then he says, ‘This is my due. I do not think that the Hour is going to come. And if am returned to my Lord, I will definitely find the best reward with Him.’ But We will inform those who are kafir of what they did and make them suffer a ruthless punishment. (Surah Fussilat, 49-50)

People who fall into hopelessness and rebellion have fallen into satan’s trap and are obeying his command. But believers, who are always optimistic and look hopefully toward the future win Allah’s approval and the merit of the Hereafter, as well as living a healthy and happy life in this world as a blessing from Allah. Since they are optimistic under all circumstances, cling tightly to the Qur’an and close friends of Allah, satan will be unable to deceive them and inflict despair upon them.  Since this is one of the important issues that constitute the essence of the moral values of the religion, believers are very scrupulous regarding it, as they are in all other Qur’anic matters.

Another aspect of the subject is that satan, who is unwilling for anyone to live by Allah’s religion, always wants people to adopt irreligious life styles, of which model pessimism is one component. So much so that in some societies pessimism literally becomes a philosophy of life. People whom satan manages to bring under his influence come to delight in songs, films and writings that express pessimism and despair.

Yet pessimism is incompatible with human reason, logic and the power to make healthy decisions. Pessimism damages mental and physical health and is a psychological disorder that can even lead to suicide, depending on its severity. One cannot, of course, expect such people to live by the moral values of the Qur’an. And this suits satan’s purposes very well. Because in this way he leads people astray from the moral values of the religion in such a way that they have no expectation of the Hereafter, and condemns them to eternal suffering alongside him. This has been satan’s greatest aim throughout the course of human history.

A hopeless person also spreads negativity and pessimism to those around him. With this attitude he literally acts like satan’s helpmate. Because through him satan encourages the kind of state of mind he wants to instil in people. By adopting such an attitude, a person has, willingly or otherwise, entered into the service of satan. But man is created to serve Allah and His religion, not satan.