We don’t fight for victory over sin as New Creations in Christ, we fight the good fight of faith from the victory already accomplished for us in our union with Christ. On the Cross Jesus didn’t just die for our sin; He took us in His person to the Cross, and In Him we died to sin.
His victory over sin, became our victory over sin, because we (The Old Man or Old Self), died in Him. Again, you don’t work toward victory, or even believe for victory; instead, you believe from victory. We don’t achieve it, because we already received it in our new birth. It’s a wonderful truth to know that the next time you get tempted, remembering that you have already been set free, you can restfully trust Him to manifest the victory that He has already won over that particular area.
Rom. 6:10, For the death that He died, He died to sin once for all; but the life that He lives, He lives to God. 11 Even so consider yourselves to be dead to sin, but alive to God in Christ Jesus.
1 Cor. 15:57, but thanks be to God, who gives us the victory through our Lord Jesus Christ.