Prayer isn't about convincing God to do what you want. Jesus said ask for anything in his name, which means asking according to his will, power, and authority. When prayers go unanswered, it's not that God failed you, but that your request didn't align with what he actually intends.
Christians think God is obligated to answer to their every whim. Now, the result of this kind of deception is that they become angry when he doesn't. Prayer is about aligning ourselves to the will of God, not about persuading God to do that which is outside of his will. And even when we pray in faith, this doesn't obligate God to do as we will. You can ask for anything in my name, and I will do it so that the Son can bring glory to the Father. Think about what Jesus said. He said, yes, ask for anything in my name. Well, what does that mean, in my name? In my name means according to my will, by my power, and in my authority. Importantly, according to my will.
