Paul held little hope of any intrinsic improvement of the human heart. In the above verse, he laments to the Romans that nothing good lives in him; that is in his sinful nature. The term 'sinful nature' is a translation of just one word in the original Greek -- the word 'flesh'. 'Sinful nature' is an Augustinian term, coined in the fifth century and has served as a useful description; but has also led to the idea that Christians have two natures, a fallen nature we inherited from Adam and a new nature that seeks to be obedient to God, the giver of our new nature through the "born again" experience. The word 'flesh', however, when it occurs in this context, doesn't refer to the physical body, but to all that a person is in themselves apart from the presence of God. To live 'in the flesh' is to live in a spirit of independence and self-reliance rather than a spirit of dependence on and obedience to God. It refers to the bankruptcy of human resources and capabilities when detached from the enabling grace, presence, and power of God.
It is this sense of despair over any hope of the natural person being able to function as God intends on the basis of human capability that lies behind Paul's view of humanity. This may at first seem a rather pessimistic view, but it is entirely realistic and accurate. Apart from: (1) revelation of this in Scripture and (2) God's provision of the Holy Spirit, we would not have the grounds nor the courage to face this truth about the human condition. Jeremiah wrote long before Paul's day, "The heart is deceitful above all things and beyond cure. Who can understand it?" (Jeremiah 17:9).
Because there has been a widespread misunderstanding of Romans 7 and Romans 8, there have been at least nine 'movements' organized to explain the desire to be 'holy' and acceptable to God and yet still sin. As a result, many Christians have become disillusionment with the Christian life. Many new Christians had the expectancy that given time, discipline, and the grace of God, our hearts would somehow improve and our natural selves would grow in godliness. But this viewpoint is not true to Scripture. The Christian life does not involve eradication or the suppression of sin, but involves the counteraction of sin accomplished through the indwelling presence and power of the Holy Spirit.
It is at the point of new birth when the Holy Spirit comes to indwell a person that there begins a civil war in the soul (in our mind, will, and emotions); which is an ongoing battle of the flesh warring against the Spirit. Paul writes in Colossians 1:27, "Christ in you, the hope of glory." Glory (the moral character of God) can only be expressed by the indwelling life of Christ who is the exact radiance of God's glory. In Him, we have our sole means of victory over the flesh for in the sight of God, we are clothed in the righteousness of Christ, and our sin done away with. When we became a believer, the righteousness of Christ was imputed to us so that we would have a sure confidence in approaching God. This inputted righteousness also creates within us a desire to please God which continues to grow within us if we really are a Christian.
Paul's statement above tells us that it is impossible to live the Christian life in our own power. We do not have the power. But the needed power lives within us that can produce a truly Christian life. The war in the soul will be won when the believer truly desires to be obedient to God in every area of his/her life and begins to willingly cooperate with the Holy Spirit in His transforming of the believer into the moral image of Christ accomplished not through the human power (self-effort) of the child of God, but through the presiding power of the Spirit which is worked out in the child of God.
Romans 7 is the plea for help. Paul saw how he could not accomplish the required righteousness he desperately sought through his own self-help methods he practiced as a Pharisee and cries out, "Who will deliver me?" Romans 8 sets the heart and soul of the believer free -- "For there is now no condemnation for those who are in Christ Jesus.'' Beloved, you are destined to be mature sons and daughters of the living God. The same power that raised Christ to life after His death on the Cross is the same power that will transform your soul (you mind, will, and emotion) into the moral image of our elder Brother, Christ Jesus our Lord. Perhaps the first step toward your revealed life in Him is a simple, repentant prayer: "I know how futile it is to try living a godly life on my own. I ask that You reign powerfully in me so that my life becomes more and more a reflection of You. Thank You, Lord."