Isn't that a teaching of Jesus?
> 9 “Which of you, if your son asks for bread, will give him a stone? 10 Or if he asks for a fish, will give him a snake? 11 If you, then, though you are evil, know how to give good gifts to your children, how much more will your Father in heaven give good gifts to those who ask him! (Matthew 7:9-11)
> He replied, "Because you have so little faith. Truly I tell you, if you have faith as small as a mustard seed, you can say to this mountain, 'Move from here to there,' and it will move. Nothing will be impossible for you." (Matthew 17:20)
So why don't you believe in that?
I'm an atheist and can certainly see why it'd be silly to think that if you just pray hard enough god will grant your desire, but that's what the bible teaches. Otherwise, what's even the point of prayer?
And before you say "Oh, it was metaphorical" I'd point out the Lord's prayer where Jesus specifically prays for food. (Give us this day our daily bread). What is more good than for god to give a starving person food? Yet plenty of Christians starve, is it because they didn't believe enough?