John is instructing us about the obligation we have due to receiving atonement through the sacrifice of Jesus Christ. Forgiveness does not remove from us the obligation to keep the commands of God. The law of God is not done away once we are under the blood of Jesus Christ. His death paid for our past sins. Though His death will pay for sins committed after our original forgiveness, we are urged not to break God's laws. Sinning without serious regard and deep appreciation for Christ's death brings us into danger of committing the unpardonable sin (Hebrews 10:26, 28-29). A disciplined and robust effort to obey God's commands witnesses to Him the depth of our appreciation for the grace He gives through Christ.
John W. Ritenbaugh
The Offerings of Leviticus (Part Six): The Sin Offering
Self-deceit is an inherent part of man's emotional, mental, and spiritual makeup. We have a hard time seeing it in ourselves because we are experts in hiding reality from ourselves and trying to hide it from others. However, we fool ourselves if we think we can hide our true nature from God.
Overcoming (Part 1): Self-Deception
Other Forerunner Commentary entries containing 1 John 1:8:
1 John 3:24
1 John 5:16-17