1 John 3:19-20
 By this we shall know that we are of the truth and reassure our heart before him;  for whenever our heart condemns us, God is greater than our heart, and he knows everything. (ESV)
We are told in modern music, movies, and other media to "follow our hearts." It makes us feel good to know that our heart will guide us. Whatever we feel is what we should do. There is a small problem with this plan, however. The Word of God tells us that our hearts cannot be trusted! Listen to what the great prophet Jeremiah says about the human heart:
 The heart is deceitful above all things, and desperately sick; who can understand it? (ESV)
So, then, how can we know that we belong to God? How can we know that we are of the truth? How can we be reassured of our standing with Him? Our hearts, instead of being trustworthy in leading, actually condemn us. The Apostle John declares, "God is greater than our heart, and he knows everything."
The truth of God being greater than our hearts is a great comfort. My heart, or my emotions, are all over the place. God is constant. He is always true. His Word is truth. If God says that I belong to him, I do not need to look to my heart for assurance. For the believer in Jesus Christ our assurance comes from God himself. And how does he let us know? First of all, in his written word. Secondly, he assures us with His Holy Spirit. Paul tells us this in Romans 8:
 The Spirit himself bears witness with our spirit that we are children of God, (ESV)
We can be assured of our standing with God with the truth of His Word and the presence of the Spirit. Don't follow your heart. Your heart cannot be trusted.