In this verse, believers are urged to live according to God's guidelines. The sacrifice of Christ removes the eternal penalty of all sins, whether past, present, or future. More importantly, those who place their trust in Christ will be forgiven even if they are unaware that they have committed a sin. Those sins we become aware of should be confessed, and we will be forgiven as a result. In obedience to God, whatever we lack, He will make up for.
As children of God, we are also children of light. Through salvation, we were transferred from the kingdom of darkness to the kingdom of the dear Son of God. Therefore, we are expected to walk in the light as He does. However, the world tries to squeeze us back into its mold, and the enemy of our soul tries to lure us back into the destructive circle of darkness and sin.
God is the purest light. All His children are protected and joyful when they remain in fellowship with Him and walk in the light of His love. By choosing to live in the light, a sinner has made a sweet communion with the great Father of light, life, hope, and love.

Dear Heavenly Father, thank You so much for the blood of Jesus that cleansed me from all my sins and identified me with Christ's righteousness. The grace of God gives me the option of walking in Your marvelous light or in the shadow of the world, the flesh, and the devil. As of today, I choose to walk in the light as Jesus does in the light because I desire an even deeper relationship with Him. 
In Jesus's name I pray. Amen.