Pauline metaphor for sanctification drawn from changing clothes. Greek apothesthai ("put off, take off") paired with endusasthai ("put on, clothe with"). The imagery appears most systematically in Ephesians 4:22-24 and Colossians 3:8-14: put off the old self — corruption, lying, anger, malice, sexual immorality, filthy speech — and put on the new self — compassion, kindness, humility, meekness, patience, forgiveness, love. Scripture never presents sanctification as purely subtractive (stop sinning) or purely additive (become more loving) — both always go together.
The Christian life is a wardrobe exchange. Every sin you identify demands two moves, not one. Put off the old clothing and put on the new. Merely trying not to be angry produces a vacuum; put on kindness to fill it. Merely trying not to lie produces a scrupulous, silent anxiety; put on truth-telling as a positive practice. The structure assumes you already have the new clothes — they are purchased for you in Christ. You are not asked to manufacture virtue out of raw willpower; you are asked to wear what Christ has already provided. This is why Paul says "you have put off the old self... and have put on the new self" (Colossians 3:9-10, past tense) and "put on then" (v. 12, present imperative) — the positional already accomplished, the progressive ongoing. Practical application: make sin-killing active, not just reactive. Don't just avoid lust — pursue purity and admiration of your wife. Don't just avoid gossip — pursue edifying speech. Don't just avoid laziness — pursue diligent service. Every old garment peeled off should leave you cold until the corresponding new one is on.