Romans 8:5-8 "For those who are according to the flesh set their minds on the things of the flesh, but those who are according to the Spirit, the things of the Spirit. For the mind set on the flesh is death but the mind set on the Spirit is life and peace, because the mind set on the flesh is hostile toward God; for it does not subject itself to the law of God, for it is not even able to do so, and those who are in the flesh cannot please God."
It seems that these verses indicate that "the flesh" refers to one who is not truly saved.
Note: Mind set on flesh =
1). Death
2). Hostility toward God
3). Not able to subject itself to God
4). Unable to please God
Of course there are many parallels to a truly saved individual who is not walking according to the Spirit. That man is still at enmity with God, could ultimately die because of sin (though it would not necessarily be eternal death), and is most assuredly unable to please God, for God is never pleased with sin. "If I regard wickedness in my heart, the Lord will not hear" (Ps. 66:18).
Or, what about James 4:4 - ". . .do you not know that friendship with the world is hostility toward God? Therefore whoever wishes to be a friend of the world makes himself an enemy of God." These verses speak of one who has a relationship with God. Therefore, the truth of Romans 8:5-8, though it clearly seems to be talking about unbelievers, has dramatic parallels to the believer. The only place where there would be a difference would be on the third point - "not able to subject itself to God," for the true believer always has the ability to turn from his sin and confess them from a heart of true repentance (1 John 1:9) to restore fellowship with his Creator!
Flee immorality (1 Cor 6:18)
Flee from idolatry (1 Cor 10:14)
Flee from these things (speaking about things that would take us away from the true doctrine of Christ, and more specifically money - which is "the root of all sorts of evil") - (1 Tim 6:11)
Flee from youthful lusts and pursue righteousness, faith, love and peace, with those who call on the Lord from a pure heart. (2 Tim 2:22)