God is light

1 John 1:5-10
God is light; in him there is no darkness at all.
Walk in the darkness but we claim to have fellowship with him, we lie.
If we walk in the light, as he is in the light , we have fellowship with one another. The truth is in us.
If we claim to be without sin, we deceive ourselves and the truth is not in us.
If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.

Why?
God is light, if we claim fellowship with him, we should walk in the light, as the Lord in the light. purify and in the truth.
What is the message? First, that 'God is light'. This is the light that generates life and dispels darkness.  Anyone who claims  'fellowship' or communion with God yet lives 'in the dark' is telling a lie.
But to say we never sin is equally false. If we live in the light we will recognize and confess our sins. God can be relied on to keep his promise of forgiveness and cleansing.
How?
Confess our sins, I am a sinner, but for the grace and forgiveness, I may walk in the light. Our flesh body is easy fall into the sin, only rely on Jesus can help us away from the sin.