The human heart was created first for man's relationship to God. But sin corrupted the heart and man stopped loving God to live in disobedience. And yet it is the heart that God appeals to in His invitation for us to come back to Him through the Lord and Saviour Jesus Christ. It is the story of God's love to us through the sacrifice of His Son that, when considered, has power to turn the heart to God.
The greatest danger for any human being is that the heart, already sinful, become hardened - unmoved by the love and grace of God. God can forgive and wash away any sin by the power of the shed blood of His Son. God can turn the worst sinner who simply trusts Him into His own dear child by His miraculous saving power. But what can be done when His Word and His love is repeatedly, wilfully refused?
The human heart can become like a stone, unwilling and unable to free itself from sin despite the sober warnings of an eternity in the fiery lake for those who die without Christ. Sin has terrible addictive power. "I hearkened and heard, but they spake not aright: no man repented him of his wickedness, saying, What have I done? every one turned to his course, as the horse rusheth into the battle" (Jeremiah 8:6).
It is a serious thing to say no to God's love in Christ. It is a serious thing just to put Him off. The Bible says that out of the heart are the issues of life. A bad heart closes the door to what every sinner needs most, the mercy of God. The gracious offer of eternal life from God always impacts the heart. Receiving it gives a new heart, and refusing or ignoring it makes the heart harder.