This is what the unpardonable sin ultimately accomplishes. Through willfully practicing sin, the sinner rejects the very basis of his covenant with God, the blood of Jesus Christ. If one deeply appreciates and values His sacrifice, he will not willfully practice the very actions that made that sacrifice necessary. God forgives with the understanding that the one forgiven has turned from sin and will continue to overcome it.
When God designed this creation, He considered His purpose along with our free-moral agency. He concluded that He had to devise a payment for sin so profound in its implications that the heirs of salvation, out of overwhelming gratitude, would drive themselves from sin. Such a price of redemption could not be the death of any common person or animal, for these have neither the worth nor the ability to pay for all sin. Only the sacrifice of the sinless God-man, Jesus Christ, could meet these qualifications.
What we see in Hebrews 10:26-29 is the end of a person who, by the very conduct of his life, reveals his pitiful assessment of that sacrifice. The author makes a three-fold indictment against this person. First, he repudiates the oath taken at baptism. Second, he contemptuously rejects Christ. Third, he commits an insulting outrage against the merciful judgment of God.