big question & tough to answer. 1st: if atheists are praying to God, God will not hear their prayer. ( John 9:31 ). 2nd: its certainly seems most of the time believers do not know what is right for them, especially in the future. God's infinite wisdom is so beyond us we can't fathom it or understand it. 3rd: if God answered us why He didn't give us something, we, upon hearing His answer, would say, "oh yeah God, you are right"!!! 5: learn this verse, John 14:13- "and whatsoever you ask in MY NAME, that will I do that the father may be glorified in the Son". what we ask for isn't what is always in God's name. 6: if someone is experiencing great trouble in the receiving of what's asked for, ask God what he wants for you! too, 1st John 3:20-22 lends a helping hand here: "if our heart CONDEMN us, God is greater than our heart & knoweth all things, if our heart CONDEMN US NOT, then have we confidence towards God........."