To restate the typical presentation of the gospel slightly, each of us on this earth is born with a global orientation toward sin, which manifests itself in various specific orientations toward particular sins—some stronger than others, some wider-ranging than others, some more fundamental than others, but all of them representative of our general inborn orientation toward rebellion and wrongdoing.
Jesus Christ was God become human. He lived a fully human life, but without that orientation toward sin; he was perfect, oriented totally toward God and his goodness and holiness. As such, he was innocent of any rebellion and wrongdoing. He died on our behalf to take on himself and pay in his own body the penalty for all of our sin; he then rose again from the dead to break the power of sin and death over us; he returned to the throne room of heaven to be our advocate with God the Father; and when he had done so, he sent us the Holy Spirit to live within all those who follow him, so that we might always be connected to his presence and power.
As such, Christ is at work in his people by the will of God the Father and the power of his Holy Spirit to reorient us away from sin and toward God. The work of sanctification is nothing less than a total change of orientation, replacing the sinward orientation with which we are born, to which we are accustomed, within which our mental, emotional and spiritual habits have been formed, with the Godward orientation that is the way of Christ, which is the way of the cross.
This is hard. The grace of God is not about leaving us as we are, or making us comfortable, or protecting us from pain; this is one reason why we resist true grace and prefer a counterfeit of our own making. This is why, as Flannery O’Connor said, “All human nature vigorously resists grace because grace changes us and the change is painful.” But as painful as it may be to allow God to change our orientation, it is necessary, because the orientation with which we’re born points us, in the end, to nothing but darkness and death. It’s only if our souls are turned, if God reorients us to himself, that we can find light and life in his presence.