Your “old man” is a mindset, your way of thinking before you are converted. It is the mindset that allows your lusts and desires to rule in your life; you have not made a firm decision to fight against sin. The “new man” is your mindset after you are converted. 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 own will or the lusts and desires from your flesh (your sinful human nature). The old man is “put off”, and the new man is “put on” in an act of faith, and baptism is the symbol thereof. (Romans 6:1-6; Ephesians 4:22-24; Colossians 3:9-10.)