1) We are often deceived by our own biases and flawed perceptions of reality. We don't always seek the truth and may actively deny truths we don't want to face.
2) The Bible warns that the human heart is deceitful and that we can more easily deceive ourselves than be deceived by others.
3) Specific ways the document outlines we can deceive ourselves include thinking we are without sin, that we are good enough on our own, or that we can save ourselves through works instead of grace. The only way to avoid self-deception is to accept the truth of Jesus Christ.