The heart is the center of who you are. The Bible warns us to guard the core of who we are diligently because out of the heart proceeds the manifestations of our life.
You have a new heart because of the work Jesus did on the cross. Because of His death and resurrection you are a completely new creation, forever unified with the Holy Spirit. To see clearly the truth of who you are and all you have because of Jesus is to live fully and free. What you believe about Jesus will determine what you believe about yourself.