"God couldn’t forgive my sin."

Those who think they are too sinful for God to accept them don’t understand how merciful God is. The Bible says that He is "rich in mercy" (Ephesians 2:4). The Scriptures also tell us that "the mercy of the LORD is from everlasting to ever-lasting upon them that fear him" (Psalm 103:17). God was merciful to King David and forgave him when he committed adultery and murder. He forgave Moses when he committed murder. He also forgave Saul of Tarsus for murdering Christians (Acts 22:4).

God promises to save "all" who call upon the name of Jesus (Romans 10:13). Those who think this promise isn’t worth the paper it’s written on are calling God a liar (see 1 John 5:10). Jesus shed His precious blood to pay for their sins. Wasn’t it good enough for them? It was good enough for God. God commands them to repent. To offer any excuse is to remain in rebellion to His command—no matter how "noble" it may seem to say that they are too sinful.