One of the greatest impediments to growing in prayer is undoubtedly this: not knowing if what is asked is in accordance with God's will. As long as a person has doubts on this point, they will not be able to have the confidence to ask with the conviction that they will surely receive what they ask for.
The Bible says: "If we ask anything according to his will, he hears us." A big mistake is that children of God do not truly believe that it is possible to know the Father's will. What we need to learn clearly is how the Father guides His children, who wait and are willing to learn, that their requests are in accordance with His will.
In this wonderful book, "Prayer in Harmony with God," Andrew Murray teaches us how to pray in God's will so that our prayers may be answered.