2 Corinthians 5:17, “Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come.”
There is a danger in believing that once we have become followers of Christ, the necessary change has taken place and we have no further role to participate in.
Yes, we are new in Christ, and this calls for an ongoing change to become more like Him. This process is called sanctification. Part of our sanctification includes putting off sin and putting on that which pleases Christ.
It involves killing the sins and wickedness that characterized us before we were saved. At the same time, we are also putting on Christ-like holiness as we behold our Savior and His work in the gospel.
This task cannot be done without Christ’s grace as we must work simultaneously at putting off the characteristics of our old-selves and putting on the characteristics of the new-selves, as one without the other is not effective.