Yours is a false dilemma fallacy. While it is true that habitual sin is the mark of the unsaved, it is also the mark of the saved person who subsequently chooses to habitually sin. Believers always have the choice whether to sow to the flesh or sow to the Spirit.
Paul warned the brethren in Rome "For if you live according to the flesh, you will die but if by the Spirit you put to death the misdeeds of the body, you will live. Rom 8:13. Spiritual death is referred to here as everyone physically dies no matter what kind of lifestyle they lived.
There are also 2 ways you can read Romans 8:1-2, of course one is wrong.
Romans 8 New King James Version (NKJV)
Free from Indwelling Sin
1 There is therefore now no condemnation to those who are in Christ Jesus, who do not walk according to the flesh, but according to the Spirit.
2 For the law of the Spirit of life in Christ Jesus has made me free from the law of sin and death.
The wrong way is saying 'who do not walk according to the flesh, but according to the Spirit, as if this is a personal daily choice they make. One day they walk according to the Spirit, and another according to the flesh, that's just real bad theology.
The right understanding is they are in Christ and Christ is in them, so they then walk according to the Spirit with their life and practice, because they belong to Him and he directs their steps. In another place it is said, and those who are Christ's have crucified the flesh with its lusts and desires. And a good tree cannot bear bad fruit, and a bad tree cannot bear good fruit, yet people frequently contradict Christ by saying yes they can.
Agree with Christ otherwise you know nothing.
And the following verses clearly point out your either in Christ or your not in Christ, there is no in one day and out the next, and then back in again. He doesn't indwell you and then fly out and then come back again.
Believers wont be carnally minded, as that would mean they are at war with the Holy Spirit.
And if anyone is in Christ he is a new creation with all things become new, and the OLD WAY IS GONE.
He condemned sin in the flesh, 4 that the righteous requirement of the law might be fulfilled in us who do not walk according to the flesh but according to the Spirit.
5 For those who live according to the flesh set their minds on the things of the flesh, but those who live according to the Spirit, the things of the Spirit.
6 For to be carnally minded is death, but to be spiritually minded is life and peace.
7 Because the carnal mind is enmity against God; for it is not subject to the law of God, nor indeed can be. 8 So then, those who are in the flesh cannot please God.
9
But you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. Now if anyone does not have the Spirit of Christ, he is not His.