Remember, you are an adopted son.
When you come to Him, you do not have to pray yourself into His favor - you are already there. He wants to bless you with every heavenly blessing. And, because His best for you is higher that your concept, the thing you want may not come about.
It does not mean that you have prayed wrongly. It does not mean that you don't know the situation. It simply means that the One who sustains the universe with His Word of Power loves you enough to give you the best.
He said He would not withhold any good thing.
Believe Him.