It is sin! That is what this dark heart reminds us of. Sin can never be in Heaven.
The Bible says, “All have sinned” (Romans 3:23a). That means everyone—you and me. Everyone is born with sin inside of them that makes them want to do wrong. Nobody had to teach you how to disobey or to tell lies.
God says that sin must be punished. The punishment is to be separated from God’s love and help now on Earth and later to be separated from Him forever if your sin is not forgiven.