contrary to modern mainstream teachings, sanctification is a process.You have to read 1 John 3 and all its verses in context.
8 He who sins is of the devil, for the devil has sinned from the beginning. For this purpose the Son of God was manifested, that He might destroy the works of the devil. 9 Whoever has been born of God does not sin, for His seed remains in him; and he cannot sin, because he has been born of God.
You may be shocked to know that 1 John 1:9 9 If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.
is the same as Acts 2:38 Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit.
Both verses are to become a Christian and receive the gift of the Holy Spirit.
1 John 1:9 is not a get out of jail free card in a demonic cycle of sin, repent, sin, repent, sin, repent, sin, repent ad infinitum as most denominations teach. I believe the Word, not denominations of man.
James 3:2 makes clear that we all stumble often. we then confess and pray for help, we repent more and more all the time of old habits and possibly even addictions via assistance of the Holy Spirit.
we work our way gradually more and more toward the perfection spoken of in Matt. 5:48 (possibly more of a spiritual perfection of the heart than man's idea of never ever stumbling)
Jesus' blood is our advocate with the Father.
but that doesn't mean we "get saved" and then continue to live as we've always lived with some spiritual pass to sinning.
what is the Biblical definition of sin?