There are several matters here that are crucial -
First, 1 John 1:8 should never be read without also reading 1 John 1:10 -
8 If we say we have no sin [noun], we deceive ourselves, and the truth is not in us. ... 10 If we say we have not sinned [verb], we
make Him out to be a liar, and His word is not in us.
Thus we are all sinners both because of what we are - in a state of sinfulness; and because of what we have done - committed sinful acts.
Second, let us examine 1 John 3:9 according to the more literal BLB -
Anyone having been born of God does not practice sin, because His seed
abides in him, and he is not able to continue sinning, because he has
been born of God.
There is a similar statement in V6 -
No one who remains in Him keeps on sinning. No one who continues to
sin has seen Him or known Him.
Both V6 and V9 imply that a committed Christian lives a perfect sinless life!! Is this possible?
Yes and no. Certainly, a person fully committed to Christ does not sin - but that is the crucial point - it is only a person fully committed to Christ is sinless and perfect - but who is fully committed to Christ? Unfortunately, John also says about us 1 John 2:
15 Do not love the world or anything in the world. If anyone loves the world, the love of the Father is not in him. 16 For all that
is in the world—the desires of the flesh, the desires of the eyes, and
the pride of life—is not from the Father but from the world. 17
The world is passing away, along with its desires; but whoever does
the will of God remains forever.
Thus, the life of the Christian is often one of being distracted by the desires of the flesh, the lust of the eyes, and the pride of life. If we keep our eyes fixed on Jesus (Heb 12:2) and do not get distracted by the things of this world, we would be sinless.
Therefore, the focus of the Christian life is NOT to keep the law but to keep our eyes upon Jesus:
Heb 12 - 1 Therefore, since we are surrounded by such a great
cloud of witnesses, let us throw off every encumbrance and the sin
that so easily entangles, and let us run with endurance the race set
out for us. 2 Let us fix our eyes on Jesus, the author and
perfecter of our faith, who for the joy set before Him endured the
cross, scorning its shame, and sat down at the right hand of the
throne of God. 3 Consider Him who endured such hostility from
sinners, so that you will not grow weary and lose heart.
As sinners - we keep getting distracted and sinning.