In Deut. 4:29 we read "But if from thence thou shalt seek the LORD thy God, thou shalt find him, if thou seek him with all thy heart and with all thy soul." The heart is an important aspect of answered prayers. In fact, prayers can be described as a "heart-cry." Psalm 62:8 says "Trust in Him at all times; ye people, pour out your heart before Him: God is a refuge for us. Selah" The Bible tells us that God is the one who searches our hearts (see 1 Chr. 28:9; Ps. 139:1, 23; Jer. 17:10; 1 Cor. 4:5; Heb. 4:12-13). Jesus describes the heart of those who say they are believers but in reality are not in Matt. 15:8, here Jesus gives us insight into their hearts, mind you only God can do this: "This people draweth nigh unto me with their mouth, and honoureth me with their lips; but their heart is far from me."
Our hearts play a very important role in prayer. If you are going to have a prevailing prayer life, it will have to come from a clean heart. Now the Bible has stated very plainly the truth about our hearts. In Jeremiah 17:9 the Bible describes our hearts as being "decietful above all things" and "desperately wicked." This is the most natural and most sincere description of our hearts. But we as Christians are not left to such an heart. We are not to have a heart-life resigned to such conditions. The Bible declares to us that we can "purify our hearts" (see James 4:8). Not only may we clean our hearts, but rather it is a command that we should do so. And in doing so, God draws near to us.
If our hearts are filthy or sinful, God does not even hear our prayers. Psalms 66:18 says: "If I regard iniquity in my heart, the Lord will not hear me." Which 'heart' do you have? Both can and do 'pray.' Both can dutifully function the same way. But only the heart that is right with God merits God's blessing of answers to prayers. Proverbs 15:8 puts it this way: "The sacrifice of the wicked is an abomination to the LORD: but the prayer of the upright is His delight."
God delights in answering our prayers, Psalm 37:4 says: "Delight thyself also in the LORD; and He shall give thee the desires of thine heart." Again, God delights in granting us the desires of our hearts - but it must be understood that it is not because He is obligated to, as though He owes us an answer. It is not that God can be manipulated. It is not because we argue or bargain with Him or "talk Him out" of anything. Rather, as we delight in Him, He begins to influence us and change us, and that change touches our very character. Soon enough we begin to like what He likes. In other words our desires lines up with his desires. Our hearts desires lines up with His will. When this happens we can perfectly claim 1 John5:14 "And this is the confidence that we have in Him, that if we ask anything according to His will, he heareth us."