I like to think of this twofold approach of ‘puuting off’ and ‘putting on’ as represented by the two blades of a pair of scissors. We readily recognize that a single scissors blade is useless as far as doing the job for which it was designed. The two blades must be joined together at the pivot point and must work in conjunction with each other to be effective. The scissors illustrate a spiritual principle: We must work simultaneously at putting off the characteristics of our old selves and putting on the characterisitics of the new selves. One without the other is not effective.
…to put off your old self, which belongs to your former manner of life and is corrupt through deceitful desires, and to be renewed in the spirit of your minds, and to put on the new self, created after the likeness of God in true righteousness and holiness (Ephesians 4:22-24).