Struggling with Sin
Christians will always struggle with sin and that's the truth. Romans 7:14-25 is pretty much of a long passage on the fact that Christians will have their struggles and that only because they are saved by faith in Jesus Christ, the victory over sin can be win. Power over sin is NEVER without the Lord Jesus Christ because it is God that works in the believer (Philippians 2:12-13). Salvation does not merely save, it inevitably produces good works as a result of salvation (Titus 2:11-15). As said, salvation is NOT by works yet the works of man can show who is saved and who is not saved.
So now to further cut down and do concise but meaningful commentaries on the Paul's struggle with sin.
There is indeed no doubt that in the flesh, it will remain sinful and there is nothing good about the flesh nature- the old nature of the believer which has become the cause of frustrations for Paul as well for every Christian as they continue their path in being sanctified as a result of salvation. A believer in Christ in his/her new self will NEVER love sin but hate their sin. However because of the flesh, what they hate to do, that they will do and they will hate the fact that they have stumbled into sin. It is an everyday struggle for the Christian to battle against sin, to say no to sin and if they rely on the flesh, they will only end up doing what they had hated, that is sin.
The struggle is between the old man and the new man- Christians can never win the battle with sin if they trust in their flesh. Jeremiah 17:5 says, "Thus saith the LORD; Cursed be the man that trusteth in man, and maketh flesh his arm, and whose heart departeth from the LORD." As said, the flesh will really disappoint. An example would be is how David when he strayed away from fellowship with God led him to the sin of adultery with Bathsheba, which resulted to throwing his family into turmoil. Solomon because he got too confident with what God had given him ended up in the wrong alliances. Samson when he got cocky about his strength ended up misusing it to his own demise. However, because they were really believers, they really had the frustration of the fact they had fouled up, and because they were saved, they repented of their misdeeds and asked God for forgiveness. Psalm 51:10-12 says, "Create in me a clean heart, O God; and renew a right spirit within me. Cast me not away from thy presence; and take not thy Holy Spirit from me. Restore unto me the joy of Thy salvation; and uphold me with thy free Spirit." which was a result of David's being saved, not for David to be saved again otherwise it would be works salvation.
The apostle Paul also mentioned in verses 21-25 that the very inner struggle of the Christian is there, it is difficult but never impossible to overcome. What is difficult is not always impossible. Growing up in the Christian life is difficult but not impossible. On the other hand, works salvation is always impossible because of the fact that Christians are not perfect yet they are called to perfection as a result of being saved. What evidences are there of God's work in the life of the believer? Verse 22 says, "For I delight in the law of God after the inward man:" which means that as a believer, a Christian delights in God's Law. Many times im the book of Psalms that David mentions the Law of God is his delight. And in conclusion, it says in verse 25, "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." that is because one is saved, they will serve the Law of God only because of Jesus Christ who saves people from their sins.