The one whose heart is not self-willed is one whose heart is lifted in a song of prayer and praise to God daily. The heart rises in meditation upon the Word of God. In it the heart is encouraged. In it the heart is strengthened. In it the heart knows the promised blessings of God and knows what He does for His children, His people. They are those who wholeheartedly belong to Him.
It is one who knows that it is only God who performs the perfect works of God in the soul. It is one whose heart is after the heart of God. It is one who speaks, believing God. It is one who lives in the light, trusting God; for God is light and in Him is no darkness at all.
It is one who can say with the psalmist these words:
Psalm 101:1-8 KJV
 I will sing of mercy and judgment: unto thee, O LORD, will I sing.  I will behave myself wisely in a perfect way. O when wilt thou come unto me? I will walk within my house with a perfect heart.  I will set no wicked thing before mine eyes: I hate the work of them that turn aside; it shall not cleave to me.  A froward heart shall depart from me: I will not know a wicked person.  Whoso privily slandereth his neighbour, him will I cut off: him that hath an high look and a proud heart will not I suffer.  Mine eyes shall be upon the faithful of the land, that they may dwell with me: he that walketh in a perfect way, he shall serve me.  He that worketh deceit shall not dwell within my house: he that telleth lies shall not tarry in my sight.  I will early destroy all the wicked of the land; that I may cut off all wicked doers from the city of the LORD.
Let the words of my mouth, and meditation of my heart, be acceptable in Thy sight, O Lord, my strength, and my redeemer.
God is clear. He saves to the uttermost. Yet, the wicked persist to continue outside His will. God does not bless these with His promises. Therefore, they do not know His favor.
He will not force upon them His gift of salvation, nor His love, nor His gift of repentance. His mercy, His judgment, His love allows them to be destroyed by the works of their own hands.
God is a consuming fire. He only destroys sin.
God takes no pleasure in the destruction of the wicked. He cannot and will not move against His own Word, His law of love. Therefore, God does not change. He cannot and will not reverse the words that have gone forth from His mouth.
Only God—who is a consuming fire—can put an end to sin, the devils, and Satan. Once and for all, sin will be destroyed. Sin will never rise its ugly head again. By faith and by God’s grace (His Power), we will be found with the faith of Jesus, and without sin.