Eph 4:22 That ye put off concerning the former conversation the old man, which is corrupt according to the deceitful lusts;
This we must do ourselves. We put off the old man, the person we once were, with it's bad habits and incorrect thoughts. We, must put them off. Seriously, this may take time, but we are being made in his image, day by day.
Eph 4:23 And be renewed in the spirit of your mind;
Where is the power for change? It is within, the spirit of the mind. The Holy Spirit that has made you new in Christ, shall change you.
Eph 4:24 And that ye put on the new man, which after God is created in righteousness and true holiness.
Again, it is our responsibility to put on the new man in God's Spirit, which is righteousness and true holiness. True, not false, not error and corruption, but truth and incorruption. Each day we must put on the new man, much as we are commanded to put on the whole armour of God. The purpose is to be equipped to lead a holy life and to resist the old man and the devil. The world, flesh and the devil are the enemies to our new Spiritual walk in the new man. We must learn our authority and walk in it, it is our choice.