However, you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you But if anyone does not have the Spirit of Christ, he does not belong to Him.Romans 8:9(NASB)
As members of the fallen race of humanity, we were born with a fallen nature and a carnal mind that can never, ever please God, for the thoughts and the intention of man's fallen nature are only evil continuously. There is nothing in fallen man that can ever please God, and even good deeds that impress other people are not pleasing to the Lord - for the unbeliever has a fallen, carnal nature. The natural, unsaved man is dead in his sins and at enmity with God.
As born again believers, we are given a new nature (which is the very life of Christ), when we trust in Him for salvation. And although we are still able to carry out 'good' works through our sinful flesh which may impress others, they do not and cannot please God. Our mission and ministry as God's children, is to be spiritually minded Christians and not carnally minded believers. For to be spiritually minded is life and peace, but the carnal mind continues to be at enmity against our Heavenly Father.
The fallen nature of fallen man is a rebel against God and cannot ever please Him, for the fallen, carnal nature is not subject to the law of God but is a slave to Satan, a slave to sin and death. However, Paul makes a big distinction between those that saved by grace and the unsaved natural man - those that are born again and those that are dead in their sins. For those that are spiritually minded carry out their good works from their new born again nature from Christ which is imputed to us at salvation, rather than reverting back to their old, carnal nature which was inherited from Adam - a fallen, sinful nature is the birth-right of all humanity.
"HOWEVER," Paul reminds us, "you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. But if anyone does not have the Spirit of Christ, he does not belong to Him."
The major difference between the unsaved sinner and the saved saint is that the Christian has been given the indwelling Holy Spirit and a new, Christlike nature - the new, born-again life of Christ. The new nature is to grow in grace while the old sin nature is to remain nailed to the Cross, in the place of death. The unsaved man does not have the Spirit of Christ and can only function from the carnal nature which cannot please God, but the saved saint has a new nature, the nature of Christ which can only do things that are pleasing to the Lord. The old sin nature seeks remain in control in the life of a believer, but must remain nailed to the Cross for it can do nothing to please God.
Those that are saved have a new life - the life and nature of Christ which can only do good in the sight of God (although until our physical death we can choose to slip back into an ungodly, carnal mind-set.) Those that are saved also have the indwelling Holy Spirit of God Who is there to teach and train our new, born-again nature to grow in grace and in the knowledge of Christ.
The old carnal nature of the believer however, needs to be kept in the place of death. But if or when we sin, we give the old, sinful nature supremacy over our new born-again nature, which can stifle the inner workings of the Holy Spirit in our life - quenching or grieving Him and stunting our spiritual growth.
As believers, we have been lifted out of the fleshly realm and placed into the heavenly sphere. As believers, we are not in the flesh but in the spirit. As believers, we have the permanently, indwelling Spirit of God, Who has been given to us to lead and to guide our new nature in Christ so that we can be conformed into Christ's image and likeness. As believers, we belong to HIM and should not allow the flesh to usurp our privileged position in Christ. Rather, we should walk in spirit and truth so that we may grow in grace and in a knowledge of our Lord and Saviour Jesus Christ.
Heavenly Father, thank You that in Christ, I have been born from above, given a new nature, and received the Holy Spirit as a guarantee of Your eternal promise to all those who trust in Christ for salvation. May I walk in newness of spirit and do only those things that are pleasing to You. This I ask in Jesus' name, AMEN.