God alone fully understands what each one of us needs; we make mistakes continually and pray for things which would be harmful to us if we received them. Afterwards we see our mistakes and realize that God is good and wise in not giving us these things, even though we plead ever so earnestly for them.
If we pray for anything according to the will of God, we already have what we pray for the moment we ask it. We do not know exactly when it will arrive; but we have learned to know God through the Spirit of God, and have learned to leave this in His hands, and to live just as happily whether the answer arrives immediately or later.