Hebrews 10 is about the high priest on the day of atonement. We enter the holy place through our high priest's undefiled conscience. He is the one with no conscience of sin. As we abide in him, we become like him.
You treat the blood of Christ as if you were covering blemishes on your face: A little dab here, a little dab there....
How do you know when you've done enough? If you believe you have to atone for sins after salvation, you should be terrified to die - truly not knowing if you have one or several sins one your record at the moment of death.
Just one sin will damn you, because, yet again, God's standard is complete perfection.
We are to be perfect as our heavenly Father is perfect. (Matthew 5:48)
Get it? You have to be as perfect as GOD HIMSELF.
"Whoever is born of God does not commit sin; for His nature remains in him: and he cannot sin, because he is born of God." (1 John 3:9)
If you still sin (and you know you do) by God's word, you are not born of God. How do you dance around verses like that? The Lord says those who are His, cannot sin.
Cannot sin.
Cannot.