To pray properly is not any easy matter. To pour out your heart and soul before God, to believe he hears and will come to help you; to pray in faith and to wrestle with him; to strive for a blessing and hope against hope; being delayed, yet waiting for him until he comes; this is exceeding hard to be done. Our natural corruptions hinder us with dullness and hardness of heart. Guilt gives stabs to our prayers and hinders assurance. Our ignorance of the nature and method of God binders us from praying properly. We have a false image of God, and view him more like one of us, and not as one filling heaven and earth with his majesty and glory. Though he is so good to us, our prayers are weak and cold. We view delays as denials, our faith wavers and we are discouraged and give up.
The difficulty of the things we pray for also hinders our prayers. Satan always labors to oppose our prayers. He knows that if our faith does not take hold of God, then God will not lay hold on us. He strikes us at this vital point: our seeking God. He fills our hearts with cares, temptations, or discouraging thoughts of God to keep us from prayer. If we continue, he seeks to persuade us to despair that our prayers are even heard, and that God does not love us. It is one of the hardest tasks in the world to pray with faith and feeling. If you find stops and failings, do not be discouraged; you realize how hard a thing it is. Do not be discouraged as you walk with a heavy load that you must sit down once in a while to rest. If you keep trying, your striving and endeavors shall bring you through at last. The bringing forth of a prayer is much like the bearing of a child. There is much pain, anguish and sorrow, but when the child is born there is much joy. If in prayer you are troubled, realize the outcome will be for your good.
Richard Sibbes, Works, VII:242-246