From https://www.ligonier.org/learn/devotionals/genuine-conversion

Obviously, we cannot live a life of gratitude for our salvation if we have not been saved. First we must be converted—the Spirit must change our hearts, and we must hear and respond in faith to the gospel (Rom. 8:29–30). Jesus atoned for the sins of His people on the cross, but the benefits of this atonement do not become real in our experience until our conversion.

Scripture teaches, as the Heidelberg Catechism demonstrates (Q&A 86–87), that conversion is necessary to experience the blessings of Christ’s work and to do good works of gratitude. Therefore, we must understand accurately what is involved in true conversion. After all, many people think they have been converted even though they have not believed the gospel at all. The book of Hebrews warns us about such people, the professing believers who think they are Christians because they have experienced some of the blessings that come with being church members but who fall away because they are not truly in Jesus by faith (Heb. 6:1–8).

Question and answer 88 of the Heidelberg Catechism look to today’s passage to illustrate true conversion. Fundamentally, conversion is the passing away of something old and the arrival of something new. Converted people are, the Apostle Paul tells us, new creations in Christ (2 Cor. 5:17). There is a decisive break with the old way of life and an embrace of Christ and His will.

The metaphor of the old passing away and the new coming is common in Paul’s writings. Usually, it is described in terms of death and resurrection. Romans 6:1–4, for example, explains that true converts to Christ have died to sin. They have renounced their attempts to be a law unto themselves. By fleeing from sin and running to the Savior, their old selves have been buried in the grave. In turn, they have been raised with Christ. Their new selves have been raised in power, just as Jesus was raised. These new selves live unto righteousness, just as our Savior lives unto righteousness. Unlike Jesus, there will be times when the convert sins and acts like his dead-and-buried old self (1 John 1:8–9). Yet true converts will not be satisfied to remain in sin, but they will be disturbed by their law-breaking, they will repent, and they will mortify their flesh by the Spirit’s power (Rom. 8:13).