A few thoughts on this passage from John MacArthur:
Sometimes when we talk about justification, we might assume that if at some point in time we prayed a prayer and God declared us just, that’s all we need to remember. And the fact of the matter is salvation was not just a declaration, it was also a transformation. So that you are a new creation. You are not what you used to be…. I want you to understand that this is absolutely at the heart of the Christian faith. Everything we do as Christians, everything that we look at at the core of our Christian living manifests that transformation and where that transformation is not present, there is no justification.
What happened to us in this union with Christ? Sin’s power was broken. And sin’s penalty was completed. Understand that? So as a believer there are two things I know to be true about myself. One, I am not under the dominion and power of sin. Two, I will never pay the penalty for sin. It’s paid once, that settled it. How does this flesh out in my life? First of all, if I sin, who’s responsible? Do I have to sin? Must I sin? No. If I sin, who’s responsible? I am. I am. Because I have the impulses of righteousness in my new self, and because I have the indwelling power of the Holy Spirit, because I have the truth of God, all of which can lead me through temptation and out the other side victoriously; if I succumb, the burden is with me, the responsibility is with me, but I need to know that sin does not have dominion over me.
And if I am struck over and over by besetting sins, the problem is with me not with my salvation. Right? It is not that something is missing unless I’m not truly saved at all and that may be the case. If I have unbroken patterns of sin as I did before whatever spiritual experience I had, there’s evidence to indicate that I was never really saved. But if my salvation is real, besetting sins don’t speak against the newness of my life, they don’t speak against the broken power of sin, they speak against my own commitment to holy things and the responsibility is mine. So I need to know that sin does not have dominion over me.