Despite our habit of trying to present ourselves in the best light, that will never be good enough for God. Our sin-stained bodies, the evidence of our rebellious nature, cannot enter God's presence. In the same way that we must be born again to be welcomed into God's kingdom, everything that reeks of sin must be replaced before we are welcomed into Christ's physical presence. We will be changed! Note, Paul does not say we will improve ourselves, but the change will be applied to us. God will give us a resurrection body and an uncontaminated heart.