I find then a law, that, when I would do good, evil is present with me. For I delight in the law of God after the inward man: But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members. O wretched man that I am! who shall deliver me from the body of this death? I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin. Romans 7:21-25
When we are saved, we are justified in the eyes of God. Our sin is forgiven, and the righteousness of Christ is imputed to us. We are transformed into a new life and the old, dead sinful man is left behind. We are in Christ and a new creation by the grace of God. The Christian’s inner person is holy and ready for heaven. We are ready to stand blameless before God and our Lord Jesus.
But, while here on Earth, that inner person is still in sinful flesh. We will struggle with the sin and wickedness of our humanity for all our days; until we meet Jesus. Our brief time here is a grand test and though sin no longer owns us, it is still present and working against our spirit providing the opportunity for faithful obedience or failure. When believers sin we do not lose our salvation, but diminish our relationship with God. I do think that those who habitually sin, enjoying forgiveness and then returning right back to sinful pleasure bring into question the validity of their salvation.
For if after they have escaped the pollutions (defilements) of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning. For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire. 2 Peter 2:20-22
If you struggle with sin, then know that the Holy Spirit is at work in you. Those without Christ seek the pleasure of sin and there is no struggle. Our sanctification by the Holy Spirit is a work in progress throughout our life, and it is through Jesus Christ that we will be finally delivered. Until then, we go on serving the will of God, as our flesh struggles against us. Thankfully, though we are “wretched men,” the mercy of God does not end and is fresh every morning. Read Lamentations 3:22-23 For us, there is no condemnation.
Therefore there is now no condemnation at all for those who are in Christ Jesus. Romans 8:1