Why is the concept of the 'old man' important for Christians?

In Romans 6:6, Paul teaches that our 'old man' was crucified with Christ so that the body of sin might be destroyed, enabling us to walk in newness of life. This theological concept is pivotal because it illustrates the believer's transformation; upon faith in Christ, we are not merely improved versions of our old selves but have undergone a radical regeneration. The old man's death signifies the believer's departure from the reign of sin and the beginning of a new life empowered by the Holy Spirit. This distinction is foundational to understanding the ongoing struggle with sin in the life of a Christian, who is both justified and being sanctified.