Believing in Allah and the Last Day is the only source of tranquility

The only source of tranquility is believing in Allah the Almighty which leads you to obey Him, and
 believing in the Last Day which prevents you from doing harm to any creature on the earth. This profound faith should not become impure by doubt or get spoiled by hypocrisy, and man should act according to this deep faith. Actually, life has taught us that people who are anxious, distressed, confused, futile and lost are those who are deprived of the grace of faith and the calmness of certainty. 



 This feeling of tranquility is a gift from Allah the Almighty; Allah sends it to the believers' hearts to keep them firm when people get confused, to please them when people are discontented, to make them believe with certainty when the people's hearts are filled with doubt, to help them remain patient when people lose their patience, and to help them keep calm in difficult situations when people lose their mind. Thus, this feeling of calmness and tranquility is a light from Allah the Almighty which calms the terrified, reassures the worried, pleases the unhappy, gives rest to the exhausted, gives strength to the weak and guides those who go astray. This feeling looks like a gate that is made by Allah the Almighty for His believing servants to lead them to Paradise, and through it the gentle breezes of Paradise blow, its light gleams and its fragrance and aroma emanate. It is a reward from Allah the Almighty to His believing servants for their righteous deeds, and it is a sample of the bliss which is awaiting them in Paradise after their death where they can enjoy these gentle lights, fragrance, safety and security. It was said: "Indeed, there is a Paradise in the worldly life whoever is deprived of admitting to it, will never be admitted to the Paradise of the Hereafter." It is the Paradise of being close (to Allah)", and the Paradise of tranquility. Allah the Almighty says:

(And admit them to Paradise which He has made known to them (i.e. they will know their places in Paradise more than they used to know their houses in the world).)

[Muhammad, 6]

 It means they tested its sweetness in the worldly life.