…and being clothed with the new man, who is renewed in knowledge according to the image of the one that created him.
This scripture is not saying, Christianity is merely putting on a new image of yourselves, or thinking of yourself differently, its not turning over a new leaf, starting again or pulling up your socks and trying harder.
It is telling you that your new self, who got born-again when Christ came into you is in the image of God, not two arms and legs image, but identical to Him in righteousness and essence (Ephesians 4:24). God is Pure, Perfect, Holy, and is Spirit. You are the same, you are born of Him now from above and are the righteousness of God (2 Corinthians 5:21).
It is saying you need to renew your knowledge according to His image not the body/soul/heart image of your physical/soulical born of this earth life.
In simple terms it’s, saying, you are not the flesh, you are a new creation in His image understand it.
Change your understanding of yourself.