Paul states that sin cannot reign in a believer who is dead to sin, whose sinful nature has been crucified with Christ.  The evil nature and carnal inclination should not rule in the mind or body of the believer.  Therefore, we must exercise discipline and self-control to avoid pitfalls.  Since we are reconciled to God by the Blood of Christ, and we are buried with Him and raised anew in water baptism, we are automatically placed into the body of Christ (in covenant with Him).  We are to become dead to our old nature and alive through Christ Jesus.