"We have already seen that 'the old person' whom we are in Adam has been crucified with the second Adam, Jesus Christ (Rom 6:6). Hence, Paul urges believers to live on the basis of the indicative. Similarly, in Colossians 3:8-9 believers are exhorted to put off evil attitudes and actions, such as anger and evil speech. The basis for this exhortation is that they 'have put off the old person with its practices and have put on the new person who is being renewed to knowledge according to the image of the one who created him" (Col 3:9-10). Here the imperative does not take precedence over the indicative but vice versa. Believers are to remove evil from their lives precisely because they have already shed themselves of the old Adam and have clothed themselves with the new Adam....At conversion believers have stripped off the old Adam and put on the new. And since they are in the new Adam, they should live as members of the new humanity. The indicative is the basis and foundation for the imperative, and yet carrying out the imperative is not automatic. Believers face the danger of living under the dominion of the old Adam, so they must aggressively resist evil and passionately pursue righteousness." (Thomas Schreiner, Paul Apostle of God's Glory in Christ, p. 259-260)
This is a great quote from a great book by Thomas Schreiner, but more importantly it is a great truth that is easy to forget. As Christians, we are to become who we are. We are to pursue holiness because of our identity not to gain our identity. The reversal of this is living from a false Gospel even if we say we believe in the true Gospel.
What a wonderful fact to know every morning when I wake up that I wake up as a new creation because I am now in Jesus, who by his life, death, and resurrection, launched new creation. The sad thing is I often identify more with my sins then with the Savior. Holiness will not increase in my life when I self-identify myself mainly with the fact that I am a sinner. I believe the New Testament argument is that by identifying oneself as "new creation", as "saint", as "alien", as "chosen" is the way one goes about walking by the Spirit. The commands to be holy and kill sin and do righteousness are often in the New Testament not derived from the indicatives of "sinner", "creature", and "child of wrath" but from the Christians identity as a new man. The Christian life is lived by living from what the Gospel has accomplished not by living life from one's state before the Gospel. What encouragement this is!
However, make no mistake, Paul and the rest of the New Testament authors are not afraid to call the attention of their readers to there past state and former identity as "old man" and "child of wrath" and "dead in trespasses and sins". In fact, the argument of Ephesians 2 shows that Paul intentionally calls the Ephesians to remember there former way of life, but he does so in order to show the greatness of what God in Christ has accomplished by making former children of wrath into the very "dwelling place for God" by the Spirit. Nor were the apostle's naive thinking that the Christian would not sin or not acknowledge it when they had sinned. The apostle's called them to do this very thing, and then to repent and turn from their sins. The apostle's teach the inner warfare and the already and not yet in the Christian life and in all of life. But they did not call Christians to holiness by identifying Christians as unholy--they did it by calling them holy.
I found this parallel interesting today: Just as Paul calls the unbeliever who walks in disobedience and sin a "son of disobedience", Peter calls the believer a son of obedience and then calls him to obey. "As obedient children, do not be conformed to the passions of your former ignorance..." (1 Pe. 1:14). The imperatives flow from the indicative, and in the New Testament the imperatives of living the Christian life flow from the indicative of the Christians new identity in Christ. The old Adam is no longer the identity of the one who is in the new Adam. The Gospel life is lived by keeping the Gospel at the center which means Christ is the center of the Christians identity not sin. Would not the opposite be the oxymoron of Gospel-centeredness?
Therefore the Christian is to walk as a new man, as who he truly is in Christ. All the while, remembering who he once was and putting off all that came before Christ. No, the old is never to be forgotten and in fact actively remembered, but the new is always to be the Christians controlling view of himself because of the great work of God in Christ.