Corinthians 4:3-4
3 And even if our gospel is veiled, it is veiled only to those who are perishing. 4 In their case the god of this world has blinded the minds of the unbelievers, to keep them from seeing the light of the gospel of the glory of Christ, who is the image of God.
In this epistle, Paul writes that the god of this world has blinded the minds of the unbelievers. Of course he is referring to satan who continuously plants seeds of doubt in our minds. He makes us impatient when we ask for blessings and he tempts us to petition GOD for the unimportant materialism of this world. Like spoiled children, when our prayers aren't enswered in the manner that we want them to be, we often sulk and allow doubt to creep into our hearts. If we are not careful, that seed of doubt can gnaw away at our faith and before we know it, we will become atheists. Godless people.
When ever doubt creeps in due to disappointment in prayer, tuen to the Bible and seek the truth in Jesus to lift the veil thrown over our eyes by the "god of this world". The truth is simple. What we do in this world is important but what we gain in this world is not.
But lay up for yourselves treasures in heaven, where neither moth nor rust destroys and where thieves do not break in and steal. Matthew 6:20