If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness.1 John 1:9(NASB)
Although an unbeliever can gain much comfort from this verse, it is important to recognise that this is a verse that is addressed to Christians.
For the unbeliever, this verse is certainly a glorious word of truth that the one who confesses their sinfulness with a penitent heart of true repentance will be forgiven. But this truth must not be divorced from the Person and work of the Lord Jesus Christ, the anointed Messiah and promised Saviour Whose sacrificial death paid the price for our sins and Whose glorious Resurrection transferred us from the kingdom of darkness into the kingdom of God's dear Son.
We were born dead in trespasses and sins, separated from God and eternally damned, but by faith in Christ Jesus our Saviour, our sins were forgiven, all our past, present, and future sins, and we were cleansed from all unrighteousness. We became a new creation in Christ, were clothed in His own righteousness and His Holy Spirit was sent to permanently indwell our heart.
We were made one with Christ, united with Him, positioned in Him, brought back into fellowship with God our Maker, and given the right to enter the throne room of the Almighty to find grace to help in time of need. And we even became entitled to call Him 'Abba - Father' by grace through faith in Christ Jesus our Lord.
But although the power of sin was severed at the Cross, it seeks to retain authority in our lives. Although we were justified by grace through faith in Christ, we are too often willing to be influenced to sin by our old sin nature - our old Adamic nature.
Nothing can separate us from the love of God which is in Christ Jesus, and nothing can break our union with our living Lord - but sin breaks fellowship with the Father. Sin severs our communion with God. Sin is the barrier that the Christian can erect which breaks our sweet fellowship with Himself and cuts us off from communion with the Father. BUT if a Christian confesses their sins, God is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.
Although our post-salvation sins were forgiven forever at the Cross of Christ, fellowship with the Father is broken when we allow the old sin nature to direct our lives, which means that the communion we once enjoyed with Him is broken. But if we take every thought captive to Christ, walk in the light as He is in the light, and if we confess any sinful acts and attitudes (whether they be wrong things that we have done or godly things that we have not done) God is faithful and just to forgive us our sins, to cleanse us from all unrighteousness, and to remember our sin no more.
Heavenly Father, thank You that when Christ died, He paid the price for my sins and broke the power of sin in my life. In Him, I have fellowship with You and free access to the throne of grace. I confess that I have not always walked in spirit and truth but have given in to the temptations to follow the desires and cravings of my own heart. I am sorry for doing things that were displeasing to You and omitting to do those things that were pleasing to You but thank You that You are faithful and just to forgive all my sins and to keep on cleansing me from unrighteousness. In Jesus' name, AMEN.