Again, even if you don’t believe you have a duty to yourself and to God to do the right things, whether you believe in sin and God’s judgment or not, you will benefit from righteous behavior.  If you disregard doing the right thing for its own sake, people will constantly disrespect you.  For someone who believes that this world and their ego is all there is, disrespect is worse than death because it leads to a miserable life.  Those who think highly of you will eventually see you for who you are and abandon you.  Good people will avoid you and you will make enemies who will slander you.  No one will want to come to your aid and you will continually have to take advantage of those who don’t know you to get what you want.  Therefore, you should strive to live a righteous life whether you believe in God or not.