In approximately 730 B.C. the Lord, through Isaiah, called upon the disobedient people of Judah to forsake their evil ways.
Come now, and let us reason together, saith the Lord: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.
Through our complete repentance and the atoning blood of Christ, even our serious sins can be completely forgiven. We should seek to repent of all our sins and resolve serious ones with the proper authorities. True repentance entails Forsaking and confessing our sins and praying to our Heavenly Father with a broken heart and contrite spirit, seeking forgiveness.
Source: Isaiah 1:18; The Holy Bible: The New Testament (KJV).