I have found 2 things to be extremely helpful in overcoming sin in my life:
1) A person behaves in a manner consistent with the way in which he views himself. If you identify yourself with being a sinner who is just struggling to "get the victory" you will not be successful. You are trying to at attain victory instead of living out of the new life of victory in Christ that Jesus has obtained for you already. Your new-born spirit-man is in Christ and is already victorious over sin and is perfect. We do sin in our mortal bodies because of the flesh and our acquiescence of our minds and wills to follow the flesh. I am not saying we are sinless. The problem is with the yet-to-be fully sanctified flesh and our minds which are still in the process of being renewed. Your spirit is in Christ and is the REAL YOU. It is perfect. Identifying with the spirit man in Christ is the normal Christian life. Again, I do not dispute that I have flesh which leads me to sin and I am responsible for those sins. The main point I am trying to get across is that as Christians we do not struggle and try to get victory, we stand in the victory Christ won for us. When temptation comes don't own that as something belonging to you. Refuse and reject it because it is contrary to the nature of Jesus in whom we abide and have life. This leads to my second discovery from the Bible about overcoming sin. I am going to quote J. B. Stoney here who was a 19th century saint from the Plymouth Brethren fellowship in England. In this narrative Isaac represents grace and the spirit whereas Ishmael represents works and the flesh. Keep that in mind. We begin where Isaac is "weaned" and is celebrated at a feast in Abraham and Sarah's house.
2)Isaac's place was acknowledged in Abraham's house on that day, and this drew forth the reviling of Ishmael, which the apostle calls persecution. "As then he that was born after the flesh persecuted him that was born after the Spirit, even so it is now". But how do we enjoy this practically?
This is an extremely important and interesting question for us. We first find how bad Ishmael is; the incompetence of the flesh as in Romans 7, but concurrently with it, the enjoyment of what Christ is. When did persecution, as Paul calls it, when did the scoffing of Ishmael come out? When Isaac gets his place. It was a festive day, and I dare say many could look back historically to when this festive day was known to their souls. When did you get a sense in your hearts that you wanted to be so entirely free from the flesh, that you felt you would not tolerate it any longer -- not merely as to doctrine, but that you could not tolerate it? When did you arrive at that day when you felt it was not to be tolerated practically? When you learned that the flesh was opposed to Christ, and at the same time that He was possessor of your whole heart, so that you felt the flesh had no right to be there; you do not tolerate it. Therefore the apostle says, "Not I, but Christ". I call this the coronation-day, that is, when Christ is crowned King of my heart. It is not that He has the first place there; that He always had through divine grace, but He has got every place, that is, I acknowledge His sway from center to circumference. I have found out the flesh. What then? Ishmael must go out. Well, it is not a pleasant thing to accept that I am dead, and therefore God says to Abraham, "Let it not be grievous unto thee; cast out the bondwoman and her son". That is non-toleration; I accept what God has done with the flesh. Well, what then? I am at liberty .
One may ask, Does the flesh never come again? It does, but you treat it now as an intruder; and you can say to it, You are an intruder, you have no right to come here; you are supplanted, and you have no place here. You may say, But Ishmael knows the house well; thrust out at the door, he can come in at a window. No doubt he does; he was fourteen years in it, and that is a long period. But then, I say, he has no right. I am crucified with Christ, that is the first thing. This would not suffice to keep him out, he knows how to master you too well. But also you have a new power. If you turn to chapter 5: 17, You will read, "The flesh lusteth against the Spirit, and the Spirit against the flesh, and these are contrary the one to the other, so that ye may not do the things that ye would". I have got the Spirit of God to maintain me free from the intruder, and He only preserves me from the flesh.
But someone will say, You will be very often disturbed. Yes; but what does that make me feel? It makes me feel the greatness of the Spirit resisting the flesh, which is ever intruding. But how do you keep safe? By dependence on the Spirit who is my power against the flesh. In chapter 6, the apostle says, "He that soweth to his flesh shall of the flesh reap corruption; but he that soweth to the Spirit, shall of the Spirit reap life everlasting". You see how you are brought into the new order, "everlasting life". Well, you say, What is sowing to the Spirit? I am led by the Spirit. It is a wonderful thing, I speak of it timidly, but earnestly; to think I have got such a Friend, such a Master, so to speak; but it is not a Master really, but One who identifies Himself with me, and wants to lead me exactly according to Christ.