Is it permissible to suffice with saying, "O Allah, You give me what is good for me and what is best for me, so to You be all praise," when fearing that the request might be worldly, or must one supplicate and leave the matter to divine decree?

Your act of entrusting the matter to Allah concerning what you do not know to be good is sound and legitimate. You should frequently recite the reported supplication: "O Allah, what You have provided me of what I love, make it a strength for me in what You love. And what You have withheld from me of what I love, make it a space for me in what You love."

The needs that a servant asks from Allah are of two types: 1. What is known to be purely good: Such as the fear of Allah, obedience to Him, Paradise, and seeking refuge from Hellfire. This should be asked for without hesitation. 2. What is not known whether it is good for the servant or not: Such as death and life, wealth and poverty. One should not ask Allah for these except what is known to be good therein. For this reason, Istikhara (seeking guidance from Allah) has been legislated for worldly matters.

The majority view that the one who relies on Allah and supplicates achieves benefits and repels harm that others do not, and this is the correct view upon which scholars and jurists have agreed. As for the acts of the heart, such as reliance on Allah and sincere devotion to Him, they are obligatory by the consensus of the imams of religion.