Romans 8:12-14 – So then, brethren, we are under obligation, not to the flesh, to live according to the flesh— for if you are living according to the flesh, you must die; but if by the Spirit you are putting to death the deeds of the body, you will live. For all who are being led by the Spirit of God, these are sons of God.
Living according to the flesh VS living by the Spirit. We are under no obligation to live by the flesh. It is only by the spirit that we can put to death the deeds of the body. Putting to death the deeds of the body and walking in the Spirit is depending on being led by the Spirit.
Galatians 5:16-18 – But I say, walk by the Spirit, and you will not carry out the desire of the flesh. For the flesh sets its desire against the Spirit, and the Spirit against the flesh; for these are in opposition to one another, so that you may not do the things that you please. But if you are led by the Spirit, you are not under the Law.
You can’t walk by the Spirit without being led by the Spirit. When I walk by the Spirit I won’t be walking in the flesh and won’t be carrying out the desires of the flesh. The key isn’t trying to overcome the flesh but being led by the Spirit.