But if we live in the light as He is in the light, we have fellowship with one another, and the blood of Jesus, His Son, cleanses us from all sin.1 John 1:7(WNT)
Fellowship with our brothers and sisters in Christ can be such a blessed experience, but to enjoy sweet fellowship with our Heavenly Lord is the pinnacle of being a sinner saved by grace. God is light and in Him is no darkness at all, and walking in the warmth and radiance of His perfect light and communing with Him is the right and privilege of all believers - nevertheless, fellowship with our Father is a believer's choice.
Sin is the cause of broken fellowship with God. Christians that are out of fellowship with the Lord are walking in darkness, and sin is the cause of all broken fellowship. Allowing unconfessed sin to lurk within or pretending to be in fellowship while walking in the darkness is simply a lie. Fellowship with the Father is incompatible with sin - but if we confess our sin, God is faithful and just to forgive us our sin and cleanse us from ALL unrighteousness.
Any one of us who says that we are in fellowship with the Father while walking in darkness and sin is a liar who is not walking in spirit and truth: "BUT if we walk in the Light as He Himself is in the Light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin."
During our sojourn on earth, we are living in a fallen body with a sinful nature that must be kept nailed to the Cross. We can never achieve sinless perfection as some like to teach, but can choose to live in the light by keeping a short rein on sin, dying to self, living for Christ, submitting to God, resisting the devil, and flying to our Heavenly Father to receive His forgiveness through Jesus Christ our Mediator.
When we walk in the light, we will maintain sweet fellowship with the Lord. But if we choose to step outside of the light, our fellowship with our Father will be interrupted. There are many enticements to sin and we can choose to disobey God's will for our life and foolishly step back into the darkness from which we have been rescued - but the consequences for carnality in a Christian is a loss of reward - eternally saved but a wasted life, loss of reward, and broken fellowship with our Father.
Because we are children of God, we are children of the light. At salvation, we were transferred from the kingdom of darkness into the kingdom of His dear Son and as such, we are expected to walk in the light as He is in the light. But the world wants to squeeze us back into its mould and the enemy of our soul wants to entice us away from the glorious light of the gospel of truth into the destructive cul-de-sac of darkness and sin.
But God is light and in Him is no darkness at all and those who choose to walk in darkness have, of their own volition, removed themselves from sweet fellowship with the One Who purchased them with His own blood, having rescued them from the jaws of Satan, sin, and death.
Yes, it is through the shed blood of Jesus, our Saviour, that we were cleansed at our salvation and brought into the light, and it is as sinners saved by grace, that we need to be continually cleansed of any post-salvation sin as we travel through this life. While all our sins, past, present, and future, were forgiven the moment we trusted Christ for salvation, we need to confess any post-salvation sin to our Heavenly Father in order to be returned into fellowship with Him - for sin is the cause of broken fellowship.
God is love and peace and hope and joy – and God is purest light. He knows that the perfect place of protection and joy for all His children is to remain in fellowship with Him and to walk in the light of His love, just as He is in the light. When a sinner who has been saved by grace, chooses to live in the light in the same way that God is in the light, he has made a wise decision, for he will not only enjoy blessed fellowship with His Christian brothers and sisters who are also living in God’s light, but will enjoy unbroken fellowship with the Lord Jesus Christ, Himself, and sweet communion with the great Father of light and life and hope and love.
Loving Father, I praise Your name for the blood of Jesus which has cleansed me of all my sins and identified me with the righteousness of Christ. Your grace gives me the choice to walk in Your marvellous light or live my Christian life in the shadow of the world, the flesh, and the devil. I choose, from this day forward, to walk in the light as Jesus is in the light, for I desire a more intimate fellowship with Him. In His precious name I pray, AMEN.