There seems to be some confusion regarding believers that sin. First, all believers sin - so I guess were talking about ourselves here. When believers sin we have an advocate with the Father... Jesus is our defense attorney! Thank God for that grace that we are assured of. But what about willful sins?
Willful sins are those sins that we willfully determine we will not repent for but continue to practice. The scarey thing about willful sins is that God didn't offer any sacrifice in the OT for willful disobedience. Look if you want but you will not find an OT offer for grace and forgiveness over willful sins.
This is because willful sins are those unrepented sins that we practice without yielding to the truth that we know from being taught the Word. The Word of God reveals that truth to us and we must adjust accordingly. It is a mistake to think that the Lord adjusts.... we are the ones who need adjustment!
The first step in the adjustment is repentance. Repentance is the reversal of all that has hindered our walk. Thieves stop stealing, slanderers stop talking junk, fornicators stop their sexual immorality, and lusting eyes learn to look away. Repentance is the 180 that God offers us. It is a U turn on a lonely stretch of highway that is going the wrong way. It is our privilege to turn around and respond to God's grace as he offers it.
The danger in ignoring this is that we can become hardened in our sin and miss the u turn opportunity. The bible clearly says that there is a sin that leads to death. It is dangerous to flirt with rebellion when the end is a Christ-less eternity.
"Today, if you hear his voice, do not harden your hearts as you did in the rebellion" heb 3.15