Therefore, since we have so great a cloud of witnesses surrounding us, let us also lay aside every encumbrance and the sin which so easily entangles us, and let us run with endurance the race that is set before us, (Hebrews 12:1)
We have a sin-nature. Everyone born after Adam (except Jesus) inherited it.Before salvation when we flowed along with everyone else int he world who wasn’t saved, we never noticed it. After salvation when we turned 180 degrees and faced the full brunt of the flow of the world’s enmity against God, then we felt it.
We feel it every day inside of us. Paul certainly did. In Romans 7:15 he pleaded out loud,
For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate.
And he definitely had been a Christian a long time and had lots of practice at it.
Believers can never conquer the sin nature. We can subdue it, wrestle with it, have some small victories over it. It might retreat to a dark corner of the heart for a while until a more opportune time, but we can’t be victorious over it.
With the Spirit’s help we can grow in righteousness, putting the squeeze on the remaining space in us that the sin-nature has to make room for. It might shrink back, but it can never leave us. Why?
The sin-nature is part of our flesh. Like this:
We can chip away at it, but the sin-nature remains an integral part of our biology.
After the resurrection when Jesus gives us new bodies in eternity, and we are glorified with no sin particle left in us, we will stand tall and proud, trophies of His glory. Like this:
Our roots in Christ, our sap His righteousness, our leaves His mercies, beautifully made and reaching for the Son.
Until then, we continue killing the sin in us-
For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live. (Romans 8:13)