1320A: As a Man Thinketh in His Heart
God is saying that the real you apart from some form of divine intervention is the most deceitful thing in all the world. Nothing else and no one else is more likely to sell you a lie than your own heart. God said it. It is not only deceitful above all things, it is desperately wicked. That means, that left to itself, you, apart from God, would do anything that would satisfy your own desires.