I often tell our people at Redeemer Fellowship that the more mature they become as Christians, the stronger their faith, the greater gains in godliness they experience, the more painful their present sins will be. The closer we get to Jesus the more sensitive we become to indwelling sin, so there is always a struggle in the believer; a war between the flesh and the Spirit. But with the struggle we also have hope. B.B. Warfield has great words on this in his classic, Biblical Doctrines.
The process by which this great metamorphosis is accomplished is laid bare to our observation with wonderful clearness in Paul’s poignant description of it, in the seventh chapter of Romans. We are there permitted to look in upon a heart into which the Spirit of God has intruded with His transforming power. Whatever peace it may have enjoyed is broken up. All its ingrained tendencies to evil are up in arms against the intruded power for good. The force of evil habit is so great that the Apostle, in its revelation to him, is almost tempted to despair. “O wretched man that I am,” he cries, “who shall deliver me out of the body of this death?” Certainly not himself. None knows better than he that with man this is impossible. But he bethinks himself that the Spirit of the most high God is more powerful than even ingrained sin; and with a great revulsion of heart he turns at once to cry his thanks to God 8 through Jesus Christ our Lord. This conflict he sees within him, he sees now to bear in it the promise and potency of victory; because it is the result of the Spirit’s working within him, and where the Spirit works, there is emancipation from the law of sin and death.
The process may be hard — a labor, a struggle, a fight; but the end is assured. No matter how far from perfect we yet may be, we are not in the flesh but in the Spirit if the Spirit of God dwells in us; and we may take heart of faith from that circumstance to mortify the deeds of the body and to enter upon our heritage as children of God.
Here in brief compass is the Apostle’s whole doctrine of renewal. Without holiness we certainly shall not see the Lord: but he in whom the Holy Spirit dwells, is already potentially holy; and though we see not yet what we shall be, we know that the work that is begun within us shall be completed to the end. The very presence of strife within us is the sign of life and the promise of victory.
B.B. Warfield, On The Biblical Notion of Renewal (In Biblical Doctrines)