What is the reason that a Muslim who trusts in Allah and supplicates to Him frequently is not successful in his life and his prayers are not answered, while a disbeliever who does not trust in Allah is successful in his life?

The reality of reliance upon Allah is to take the possible means while attaching the heart to the Causer of these means, knowing that "what Allah wills, comes to pass, and what He does not will, does not come to pass," and there is no might or power except with Allah.

This is achieved by acting upon the means that bring success, such as obedience to Allah and Taqwa (piety), for Allah Almighty said: "And whoever fears Allah - He will make for him ease in his affair."

Reliance [upon Allah] is a great path to achieving what is desired and repelling what is feared, as Allah Almighty said: "And whoever relies upon Allah - then He is sufficient for him."

Likewise, it involves persistence in supplication and seeking times when supplications are answered, for Allah Almighty said: "Call upon Me; I will respond to you," and He said: "Is not He who responds to the distressed one when he calls upon Him and removes evil?"

Along with all of this, one must be content with Allah's decree and destiny, knowing that Allah's choice is better than the servant's choice, and that He, glory be to Him, knows what is beneficial, as Allah Almighty said: "But perhaps you hate a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah knows, while you know not."