The life a Christian lives is in Christ by faith
I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me.
Our old life has been crucified* (done away with) and we now live a new life. The things of the past must be put aside: all unrighteousness, sexual immorality, wickedness, covetousness, maliciousness; full of envy, murder, strife, deceit, evil-mindedness; they are whisperers, backbiters, haters of God, violent, proud, boasters, inventors of evil things, disobedient to parents, undiscerning, untrustworthy, unloving, unforgiving, unmerciful; (Rom 1:29-31) – Christians repent of these (turn away) and if we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness (1 John 1:9).
* A metaphor – our old ways and habits are to be reckoned dead; physically we live with our sin-nature; it is the “I” in us that rises up and sins - which the Holy Spirit dwelling in us will convict us of. Pay attention to Him!