God calls us out of darkness into the light. The change is sudden and abrupt. Darkness is defeated immediately in the presence of light. That's the way God's grace changes people who have lived in darkness. It comes from "Him who called you out of darkness into His marvelous light" (1 Peter 2:9).
Jesus said, "I am the light of the world. He who follows me shall not walk in darkness, but have the light of life" (John 8:12). Christ is our light, when God effectively calls us to faith in Christ. He is the light of life. God calls us out of spiritual darkness into the light of Christ.
God calls us to the light of Christ which overcomes darkness. It is not our achievement. Rather, the light comes to us from without, changing our hearts within. The Holy Spirit reveals the light of Christ in our hearts. Then, our testimony is in these words, "I saw the light." Give all the glory to "Him who called you out of darkness into His marvelous light."
God calls us to see the light, then we are able to walk in the light. "If we walk in the light as He is in the light, we have fellowship one with another, and the blood of Jesus Christ His Son cleanses us from all sin" (1 John 1:7).