Safety and happiness are considered basic needs for mankind:

The believer responds to the call of Fitrah (natural unborn instinct which recognizes Allah), and fully
 realizes the purpose of his existence. As a result, things become crystal clear to him, and he will live under the protection of Allah the Almighty, will follow the example of Allah's Messengers, Allah's Prophets, peace be upon them, and the pious people and will be saved from the torment of uncertainty and doubt. Actually, tranquility is mentioned in many Noble Ayat in the Noble Qur'an, the most well-known of which is the following Noble Ayah in which Allah the Almighty says: 

(He it is Who sent down As-Sakinah (calmness and tranquility) into the hearts of the believers, that they may grow more in Faith along with their (present) Faith.)

[Al-Fath, 4]

 Dear brothers, there is no happiness without tranquility, and there is no tranquility without faith. The feeling of calmness and tranquility is the main source of happiness. Also, safety and happiness are the basic needs of all people in this world. In fact, Allah the Almighty grants health, strength, intelligence, wealth and beauty to many people, but He grants tranquility just to His true believing worshippers in particular. Furthermore, the feeling of tranquility is the distinct characteristic of the true believer; he is quite overwhelmed by this feeling even if he lacks wealth or good health. He will always be pleased with it even if he misses everything, while man will be wretched when he misses tranquility even if he owns everything. None can grant you the feeling of tranquility or deprive you of it, but it is available to everyone if he acts upon Allah's Orders, and so he will deserve it.