Summary: As a new creation we are not expected to live as the people of the world does.
As a new creation in Christ we are not supposed to be like the people that are not yet in Christ. We are called to be separate from the realm of darkness, as a new creation the bible records that we are now a partaker of the kingdom of the Lord Jesus Christ and now live in a kingdom of light not of darkness.
For He has rescued us and has drawn us to Himself from the dominion of darkness, and has transferred us to the kingdom of His beloved Son.
Since we have been transferred into the kingdom of His beloved Son, which is a kingdom of light, we are living in a place that is full of light and not darkness. A new creation can never be living in darkness after receiving the gift of salvation.
In receiving the gift of salvation we are now a new creation according to 2 Corinthians 5:17.
Therefore, if anyone is in Christ, he is a new creation; old things have passed away; behold, all things have become new.
This simply means in Christ we are are a new specie that had never been before! a new creation has all things new and the old things have passed away, we now are a new creation recreated by God Himself. Without been a new creation we cannot have a relationship with Christ and we cannot live in the kingdom of His Son.
We are now a new creation in Christ and as a new creation we are called to have the mind of Christ - 1 Corinthians 2:16 ; Romans 12:2 ; Philippians 2:5. The mind of a new creation cannot be as the old one anymore, we cannot have the same thoughts as we had before and we are called to renew our mind with the word of God.
Scriptures on renewing our mind.
Set your mind on things above, not on things on the earth.
Your word I have treasured and stored in my heart,
That I may not sin against You.
2 Corinthians 10: 4 - 5
The weapons of our warfare are not physical [weapons of flesh and blood]. Our weapons are divinely powerful for the destruction of fortresses. We are destroying sophisticated arguments and every exalted and proud thing that sets itself up against the [true] knowledge of God, and we are taking every thought and purpose captive to the obedience of Christ,
And you will know the truth [regarding salvation], and the truth will set you free [from the penalty of sin].
Let the [spoken] word of Christ have its home within you [dwelling in your heart and mind—permeating every aspect of your being] as you teach [spiritual things] and admonish and train one another with all wisdom, singing psalms and hymns and spiritual songs with thankfulness in your hearts to God.
Joshua 1: 8 - 9
This Book of the Law shall not depart from your mouth, but you shall read [and meditate on] it day and night, so that you may be careful to do [everything] in accordance with all that is written in it; for then you will make your way prosperous, and then you will be successful. Have I not commanded you? Be strong and courageous! Do not be terrified or dismayed (intimidated), for the Lord your God is with you wherever you go.
But you did not learn Christ in this way! If in fact you have [really] heard Him and have been taught by Him, just as truth is in Jesus [revealed in His life and personified in Him], that, regarding your previous way of life, you put off your old self [completely discard your former nature], which is being corrupted through deceitful desires, and be continually renewed in the spirit of your mind [having a fresh, untarnished mental and spiritual attitude], and put on the new self [the regenerated and renewed nature], created in God’s image, [godlike] in the righteousness and holiness of the truth [living in a way that expresses to God your gratitude for your salvation].
We as new creation should let go of our ways of thinking and doing things that are not kingdom related anymore, we cannot mix the old with the new, - Matthew 9:17, that is not possible anymore. How can we as new creations mix the old with the new?. A new creation has God in them, the word of God says so in 1 Corinthians 3:16.
John chapter 1: 1 - 5 says this:
In the beginning [before all time] was the Word (Christ), and the Word was with God, and [b]the Word was God Himself. He was [continually existing] in the beginning [co-eternally] with God. All things were made and came into existence through Him; and without Him not even one thing was made that has come into being. In Him was life [and the power to bestow life], and the life was the Light of men. The Light shines on in the darkness, and the darkness did not understand it or overpower it or appropriate it or absorb it [and is unreceptive to it].