It is wrtten:For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries. Hebrews 10:26,27
It is also written:Hebrews 6:6 - If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
Both verses show what will happen if WE continue in sin without regret which will lead to the hardness of the heart as with the Pharaoh of the EXODUS. This will eventually lead to an irreversible permanent hardness of the heart. If a child of God sins he should immediately repent and ask the Lord not to harden his heart and also ask the Lord for help not to continue in that sin. If not it will eventually lead to him or her being desensitized to sin and then a falling away and he or she will become a servant of sin.
God Bless!