"If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness" (1 John 1: 9)
Once again, the entire chapter of First John is not written to believers.
John does not say that he is a liar (1 John 1: 8), but offers an editorial statement to soften the blow of the unshakeable truth, that we have sin, and that we must acknowledge these sins.
Otherwise, there is no release from the death in trespasses which holds every son of Adam in bondage in this world:
"15But not as the offence, so also is the free gift. For if through the offence of one many be dead, much more the grace of God, and the gift by grace, which is by one man, Jesus Christ, hath abounded unto many." (Romans 5: 15)
Yet the grace of God allows us to receive Christ into us, and His righteousness and grace (Romans 5: 17)
Do we have to keep confessing our sins then? No, because righteousness is a gift, and grace is unearned, unmerited favor.
Look once again at 1 John 1: 9.
God is faithful and just to forgive us our sins, and to cleanse us from ALL unrighteousness.
How many times do we have to confess our sins to be cleansed, then?
One time -- and when we receive that Jesus became sin for us, we become the righteousness of God in Him (2 Corinthians 5: 21)
Jesus is the author of eternal salvation for all who believe on Him:
"9And being made perfect, he became the author of eternal salvation unto all them that obey him; 10Called of God an high priest after the order of Melchisedec." (Hebrews 5: 9-10)
We confess once, and in Christ we are made righteous forever!