Ask yourself, the part of you that sins, is it your flesh, or the Spirit of Christ? The flesh will die, leaving only the Spirit of Christ that will be quickened to eternal life.
When you sin now, it only effects the flesh, not our Spirit that is now protected by Christ Spirit, which can not sin.
You seem to be considering your flesh as the heart of a person, but its simply a covering that will be discarded when you die, and its what pleasures in sin in us now. When your sinful flesh dies, itll have no effect on your spirit that Christ has indwelled in you.
The Jews also worried about the appearance of the outward flesh, over the inner heart, which was what God saw, not their outward righteousness.
Well never be able to truly distinguish between the two, flesh and spirit, until our fleshly body dies, and for the first time, that burden will be gone. Well see how easy it is to be perfect, with Christ mind in us, and our earthly body gone.
No longer will it be constantly yelling at us to do this, or do that, eat this, or smoke that, or drink this, or look at that.
JH :-)