The Holy Spirit opens our eyes of understanding to walk in the light of Christ. It comes quickly to dispel darkness, through the light of Christ. Light comes to us suddenly. Darkness is defeated immediately in the presence of light. That's the way God's Son changes people who have lived in spiritual darkness. We see the truth of Christ, taking away the darkness of unbelief.
The Holy Spirit opens our eyes of understanding to see the truth of Christ. We see the light through new birth, unto faith in the Lord Jesus Christ. It is not our achievement. Rather, light comes to us from without, changing us from within. There was darkness, then there is light. The Holy Spirit opens "the eyes of our understanding being enlightened" (Ephesians 1:18).
"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). The Holy Spirit opens our eyes of understanding to see Christ as the way, the truth and the life (John 14:6). We see ourselves cleansed from all sin to walk in the light of Christ.
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). Illumination of the Holy Spirit enables us to walk in the light of Christ, by the grace of God. We see Christ dying for our sins. We see Christ as our living Lord (Romans 10:9).