I realize it is long but if you want to understand the true nature of the sin nature start by reading this.
There is no promise in the Scripture that a Christian, in this life, will ever reach the place where he will no longer sin: "If we say that we have no sin, we deceive ourselves, and the truth is not in us" (1 Jn. 1:8). There are those who teach that it is possible to have an experience of sanctification, which they call a second work of grace. It is described in the following quotation:How wonderful that would be if it were true!The heart is purified, cleansed and made holy. It is purged of that inbred sin nature; and from that time on, temptation comes only from without, not from within a heart that is sanctified. No one ever becomes so completely perfected that he is not subject to temptation. But one has greater and more glorious victory after he is sanctified because he no longer has to contend with the carnal nature. It has been removed.
The carnal nature, the flesh, never becomes sanctified: "That which is born of the flesh is flesh; and that which is born of the Spirit is spirit" (Jn. 3:6). God never builds on the old, fleshly, sinful nature. He always begins with something new. That is why Jesus said, "Ye must be born again" (Jn. 3:7). The flesh never becomes spiritual. Do not expect it to do so. The flesh in the most saintly person is the same flesh that is in the worst of sinners.
Paul likens the two sons of Abraham to the two natures of the believer: the fleshly nature and the new spiritual nature that he receives in the new birth. "For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman. But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise.... But as then he that was born after the flesh persecuted him that was born after the Spirit, even so it is now" (Gal. 4:22-23, 29). The flesh always opposes the Spirit. What are we to do? "Cast out the bondwoman and her son: for the son of the bondwoman shall not be heir with the son of the freewoman" (v. 30). Ishmael could not be corrected. He had to be cast out (Gen. 21:10). This is the way to deal with the flesh. Thus Paul admonishes, "Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord" (Rom. 6:11). The flesh cannot be overcome by eradication. It will always be there as long as we are in this earthly body, neither can it be overcome by suppression. Some have earnestly tried to gain victory by the power of their will and the energy of the flesh. The victory is seen to be only through identification with Christ. Paul said, "I am crucified with Christ; nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me" (Gal. 2:20).
Guy P. Duffield and Nathaniel M. Van Cleave, Foundations of Pentecostal Theology, (Los Angeles, CA: Foursquare Media, 2008), WORDsearch CROSS e-book, 245-246.