Your “old man” is your mindset before conversion. It is a state of allowing your lusts and desires to rule in your life; you have not made a conscious decision to resist committing sin. The new man is your mindset after conversion. It is a decision to overcome sin and live in righteousness and holiness. It is the mind to serve God and His will, rather than your will; the lusts and desires from your flesh. The old man is “put off”, and the new man is “put on” in an act of faith, which is symbolized by baptism.  (Romans 6:1-6; Ephesians 4:22-24; Colossians 3:9-10)