What does I John 1:8-10 actually mean to you?
All have sinned and fallen short of the glory of God. This is because of Adam's sin. This is the same as 1 John 1:8. Without Christ if you say you have no sin you lie and the truth is not in you. Many say they are a good person and don't need Christ. They first have to see themselves as a sinner. Then if they confess their sin, He is then faithful and just to forgive them. At that point they are given the gift of the Holy Spirit. It is they who walk in the light, and their sins are continually cleansed because they only follow after the Spirit who would never lead them into willful sin. Once washed clean you have no sin, so what good would it be to say you still have sin when you are clean? Verse 8 is not about a Christian.
I want you to look at the pattern. There is a reason 8 and 10 are not together even though they are on the same theme. You see there is a Hebrew style of writing, many actually, but this one that John is using is contrasts. Read from verse five to the end of chapter one. You will see that every other verse or thought contrasts light and darkness.
5 - God is light
7 - if you walk in the light, cleanses sin
9 - if you confess you sin, cleanses sin
6 - if you walk in darkness, no truth
8 - if you say you have no sin (without Christ's blood) there is no truth
10 if you say you've never had sin, no truth.
This is why we can say we have no sin if we walk in the light of Jesus. If we do willfully sin, that just proves we are walking in darkness and have as our father, the devil.
1 John 3:4-10 New King James Version (NKJV)
4 Whoever commits sin also commits lawlessness, and sin is lawlessness. 5 And you know that He was manifested to take away our sins, and in Him there is no sin. 6 Whoever abides in Him does not sin. Whoever sins has neither seen Him nor known Him.
7 Little children, let no one deceive you. He who practices righteousness is righteous, just as He is righteous. 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.
10 In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God, nor
is he who does not love his brother.
Again, every other thought is a contrast. Even though written in Greek, the style is Hebrew.