In contrast to putting off our old nature, we are called upon to "put on" our new nature. And the same thought pattern should apply: you were washed clean from your sins and now the thing to do is to dress in CLEAN CLOTHES!! Sensible, isn't it! And the neat thing here is that the Lord, Himself, is your tailor! He knows your measurements and just the right arrangements of clothes for you to wear to "bring out the best in you!" For the best that God has to offer is to clothe us with the righteousness of Christ and to conform us to the very likeness of Himself! Romans 8:29 makes it clear that God is "conforming us to the image of His dear Son." We're to look like Christ with our own distinct personalities. And this will affect the way we think and the attitudes we convey.
Keep in mind that the word "nature" speaks of who you really are!! In your "old nature" you lived like a person apart from God and consumed by the attitude and thinking of this world. But, now that you are "partakers of the Divine nature" (2 Peter 1:4). And that means who you REALLY ARE is God's child! And you were meant to live as a child of God. Note Philippians 2:15, "...Live clean, innocent lives as children of God, shining like bright lights in a world full of crooked and perverse people."