Can you explain the expression: He who believes in Divine Determining is saved from grief. How come the belief in Divine Determining save humans from grief?

It is the greatest source of peace for humans to believe in Divine Determining. The believer reflects upon the arrangements and ordainments both in his self and in the outer world and sees that they are all full of many a beam of wisdom and that they all result in mercy. And saying, Everything coming from Divine Determining is good. he searches for mercy and wisdom in every event that befall him.

The believer goes in for every initiative that is necessary for the bliss of both this world and the Hereafter and eventually he depends on the mercy and favor of God and finds peace. He does not grieve for what he has lost. He does not feel sorrow for the chances he lost in the past. He well knows that such expressions as if it had been that way, this would not have happened; or only if it had not been that way, that would have happened. avail no more than make the soul suffer. He casts the burden of the past and relying on God he sets out for the future with complete peace.

He does not brag about the favors, treasures, and capabilities God has bestowed upon him. He knows every good from him and finds peace. What do the unbelievers in Divine Ordaining present to the humanity?

Not to work anymore and to wander idly? Or to suffer and cry out having first complied with causes but then not accepting the result with pleasure? What benefit do they expect out of this except leading people into distress? How can they put this heavy burden upon the shoulders of this person with tender soul and weak body? Or do they expect something for their wicked intentions out of uneasy, nervous, and rebellious souls?