Whoever follows the path of sin eventually no longer knows what he is saying. Cain even thinks he can judge God’s judgments. The Judge of heaven and earth is incapable of administering the proper punishment… If indeed God cannot, then at whose mercy are you? Cain grumbles about the punishment. He ignores his guilt.
Cain appears to have a piece of Abel ("nothing") in him. He gets scared. You will not make it in life with self-confidence. There is a power stronger than you.
13 Cain said to the LORD, “My punishment is greater than I can bear.