You have heard it said; “I will come to church when I clean up my life” or “I need to change a few things first” etc. The fallacies of these statements are that, without Christ, you can’t clean up or change a thing. Hebrews 11:6: And it is impossible to please God without faith.
A change of behavior is not a change of heart. An unbeliever does not have the capacity to “mortify” or put sin to death [i.e. – clean up]. Unbelievers may suppress sin [change behavior], but they cannot kill it [Romans 1:18].
Per John Owen:
“Unless a man be a believer he can never mortify any one sin; There is no death of sin without the death of Christ.”
Putting sin to death is not the highest priority of an unbeliever. There is a proper order to these things. First be saved, and then put sin to death. Mortification in your on power is a lie. Satan would have you believe you can do it on your own: “You are a good person; you’ve done more good than bad” and other such lies. Without the Spirit, mortification is not possible: Romans 8:13 For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live.
How is one saved? By the preaching and hearing of the word, the miracle of regeneration through the Holy Spirit and accepting the righteousness of Christ by grace through faith. How does one mortify? By maturing and sanctifying in Christlikeness through obeying the simple commands of scripture by the help of the Holy Spirit.
All this is best accomplished under the discipleship, fellowship and guidance of mature believers in the New Testament church. Notice I did not say under the minister or preacher in a New Testament church. The preacher is to equip the saints for the works of the ministry. The saints [us] are to be about God’s kingdom business of making disciples.
The order of things: salvation, mortification, sanctification, multiplication and finally glorification.