Have you ever had a shopping cart with a broken wheel? You push it around and all it wants to do is run into the sides of the aisle. If you were to let the cart go, it would immediately turn and smash into that case of pickles up ahead! You are like that shopping cart! The bad wheel is your heart. It's always veering off, leading you away from what you were created to be. You were created for God's love and glory, but instead, your heart pulls you away from Jesus and into something much worse than a case of pickles.
Being a rebel at heart means that you do not have the ability to choose God or even to respond to God on your own because you are spiritually dead; we all are. Reformed theology teaches that, because we are more sinful than we could ever imagine, it can only be God who takes our sinful heart (that broken shopping cart wheel) and replaces it with one that has both the ability and the desire to seek him and to follow him. By faith in Christ, you are no longer set to smash into the aisles of sinful destruction. No, he promises to carry us in his grip of grace.