I suppose no one, however long he has lived a life of prayer, is immune to the enemy’s attack on his confidence that prayer “works.” Again and again we are tempted to feel that God is not paying attention, our prayers are futile, why should we keep on praying? Jesus told a story about a widow who made such a nuisance of herself that even a judge who cared nothing for her or for God was finally moved to action. He used this to teach us never to lose heart. “Will not God vindicate His chosen, who cry out to Him day and night, while He listens patiently to them?” (Luke 18:7). A note says that that last phrase may also be translated “While He delays to help them.” It is worth remembering, when the delays tempt us to quit praying, that He islistening patiently — paying attention when we feel He has forgotten all about our prayer, biding Histime. And He Himself is the very One, remember, who commanded us to keep on praying and never lose heart. He is listening. He will act. Do not doubt His promise.
Source: The Music of His promises: Listening to God with Love, Trust, and Obedience by Elisabeth Elliot