“And you were dead in the trespasses and sins in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience— among whom we all once lived in the passions of our flesh, carrying out the desires of the body and the mind, and were by nature children of wrath, like the rest of mankind.” Eph 2:1-3 ESV
Notice with me what this says about believers in Jesus Christ. We were ONCE (past tense) dead in our sins in which we ONCE (past tense) walked (conducted our lives, in action, in practice), following the ways of this sinful world, following the devil (Satan) who is at work in the sons of DISOBEDIENCE – among whom we all ONCE (past tense) lived (walked, conducted our lives in practice, in action) in the passions (desires) of our flesh (i.e., in sinful passions and desires), carrying out the desires of the body and the mind (making sin our practice) , and were by nature children of wrath, like the rest of mankind.
This describes the life of a believer in Jesus. Therefore, walking in sin, fulfilling the desires of our sinful flesh, disobeying our Lord, following after and walking in the ways of this sinful world, following after the ways of the devil, doing what he desires, living the life he has for us to live, and making sin our practice are all supposed to be PAST TENSE, not in the present. They are to no longer exist in our lives. Yes, we may sin once in a while (1 Jn 2:1-2), but we should not be living in deliberate and habitual sin against the Lord. Instead, we should be walking according to (in agreement with) the Spirit of God, in righteousness (Rom 8:1-17; Rom 6:1-23; 1 Jn 3:4-10).
So, if someone tries to convince you that you can believe in Jesus, have heaven secured you, have your sins forgiven, and that you can still live like you did before you believed in Jesus, they are lying to you. For, the Scriptures teach that if we walk (in conduct, in practice) according to the flesh, doing what our flesh desires, that we will die in our sins. We will not inherit eternal life with God, no matter what we professed with our lips (Rom 6:1-23; Rom 8:1-17; 1 Jn 1:5-9; 1 Jn 2:3-6; 1 Jn 3:4-10; Gal 5:16-21; Gal 6:7-8).