From Anstey’s Doctrinal Definitions:
Like salvation, deliverance is a very broad subject in Scripture, with many applications. The need for deliverance could be from trouble resulting from sin without in men who oppose the truth (Matt. 6:13; 2 Cor. 1:10; 2 Tim. 3:11; 4:17-18, etc.), or it could be the result of sin the working within the believer’s heart (Rom. 7:24; 8:2). However, when the topic of deliverance is in view, it is usually assumed to be trouble resulting from sin within the believer. This pertains to the soul’s experience of being set free from the working of the sin-nature (“the flesh” – Rom. 7:5, etc.) within, whereby he is able to live a holy life for the glory of God.
Christians, with the best of intentions, have sought to control their sin-natures in many ways—but it has only brought them frustration and disappointment. All such human efforts have been to no avail. Men have applied asceticism (flogging the body to keep the flesh down), monasticism (trying to run away from the temptations in life by sequestering oneself from society), introspection (which only leads to morbid self-occupation), psychology (the study of human behaviour), culture, etc. As mentioned, these things always result in failure. Like the demoniac in Mark 5 who could not be tamed, the flesh in man cannot be controlled by human appliances.
What many Christians don’t realize is that the blessing promised in the gospel not only has to do with deliverance from the eternal penalty of their sins (Rom. 3:21-5:11), but it also includes deliverance from the power of sin working in their lives (Rom. 5:12-8:17). It is not God’s intention to leave those whom He has forgiven, justified, reconciled, and saved, in this world under the dominion of their fallen sin-natures, and without the power to walk uprightly. Therefore, we don’t need to look to human devices and methods to control the flesh (which don’t work), but to God—He has the solution. It is all part of His gift of grace in the gospel.
The subject of our soul’s deliverance is taken up in detail in Romans 5:12–8:17. First of all, in chapter 5:12-21, we are taught that believers on the Lord Jesus Christ are no longer under Adam's headship or part of that old race, as far as their position before God is concerned. Being "constituted righteous" believers are now part of a new race of men under Christ's headship, where grace reigns through righteousness unto eternal life.
Then, in Romans 6:1-10, we are told how this transfer from Adam’s headship to Christ’s has come to pass for the believer. Acting as our federal Head (meaning that He acts on behalf of all under Him), Christ, in dying, severed Himself from the whole system of sin under Adam. In doing so, He has severed us from it too. Through our identification with Christ's death, God sees us as "dead," and thus disconnected from Adam's race and the principle of sin that dominates it (vs. 7). Furthermore, in being “raised from the dead,” Christ has entered a new sphere of life where He “lives unto God,” and that sphere is now open to all who belong to His new race (vss. 8-10). Then, in verses 11-12, we are exhorted to “reckon” (“think it to be so”) with God that these things which are true of Christ are also true of us. Thus, on account of our identification with Christ's death we are entitled to consider ourselves to be "dead indeed unto sin" but “alive unto God” in that new sphere in which Christ lives unto God. In chapter 6:13-14, we are exhorted to yield ourselves to Him and to begin practising righteousness in that sphere of life—one act at a time. And, by the repetition of good habits we become the servants of righteousness, because sin no longer has dominion over the believer.
In chapter 6:15-23, we are warned that if we choose to live in the sphere of life that pertains to the flesh, we will come under bondage to the sins that we allow. It is, therefore, imperative that we live practically in the right sphere of life wherein is a new range of objects to occupy our hearts. These things are called “the things of the Spirit” (Rom. 8:5) and have to do with the interests of Christ. They are things such as: reading the Scriptures, praying, attending Christian meetings for worship and ministry, singing hymns and spiritual songs, reading Christian literature, listening to recorded ministry, teaching the truth, sharing the gospel, fellowship, meditating on spiritual things as we go about our daily responsibilities, serving the Lord with good works, visiting, etc. When the believer lives practically in this new sphere of life, and is thus occupied with Christ and His interests, the power of the Spirit of God will be felt in his life in keeping the flesh in check (Rom. 8:13). Thus, on this principle of displacement, the flesh will not be given an opportunity to act in the believer’s life.
In a parenthesis, in chapter 7:7-25, Paul shows that this deliverance is not accomplished through human effort, but by looking to Christ and being occupied with those things that pertain to Him. When we do that, the Spirit of God will help us live the normal Christian life, which is above the impulses of the flesh. This is illustrated in chapter 8:1-16.
The great question is: In which sphere do we live our lives? By saying, "if" in Romans 8:13, Paul shows that the onus is on the believer. God wants us to be responsibly exercised about having victory over the flesh. We have to make a conscious decision to live in the right sphere of life. This comes down to a simple matter of our wills. Our problem is that we want to surround ourselves with earthly, natural, and worldly things, and to pursue them, and at the same time expect to have the benefit of practical deliverance from the power of sin that the Spirit gives. But we can't live in the shade and enjoy the sunshine at the same time. If we pamper the flesh, we’ll hamper the Spirit! It is not that we need more of the Spirit, for God does not give the Spirit in measures (John 3:34). Actually, it's the other way around—the Spirit needs to have more of us! If we yield our lives to His leading, which will always be to pursue Christ and His interests, we will not lack the power of the Spirit in our lives to keep the flesh down, and thus experience deliverance.