"..and the LORD said unto me, Let it suffice thee; speak no more unto me of this matter."
God always hears our prayers, but He sometimes denies our request. Moses experienced this. He prayed, "let me go over and see the good land that is beyond Jordan," but this request was denied. There are desires which the child of God may express in prayer and of which he need not be ashamed before God, or man, which are not fulfilled.
Our prayers may not yield the desired fruits, but they are not therefore fruitless. Unfulfilled prayers bind us to God, sometimes more than answered prayers, because those are often easily forgotten.
By unfulfilled prayers the Lord teaches His people that they must be sanctified through suffering so that they may be made to conform to the image of Christ who also has learned obedience through His suffering.
Not a single prayer, not even an unfulfilled prayer sent up in sincerity, is fruitless. Often the Lord uses unfulfilled prayers. No matter how unfathomable God's ways seem, the Lord in His incomprehensible wisdom always has the eternal well being of his Zion in mind.
Moses's unfulfilled prayer served to loosen his ties to the world. The Lord still does that with His people. If everything that man desires was granted, he would seek treasure on earth. But it is necessary to lose treasures here below in order to lay them up on high, so that we experience more and more, "Here we have no abiding city."...It is far better to walk in the Lord's ways, even though that may be a deep way, than to live according to our own desires and against God's will."
~ excerpts from the chapter, Unfulfilled Prayer in Praying Always by Frans Bakker