1 John 1:8

If we should say that we have not sin, we deceive ourselves and the truth is not in us, 1 John 1:8.

Although the sin nature has been rendered ineffective in Christ when we walk by the Spirit (Romans 6:6), there are still times in our lives when we set our minds on the things of the flesh, resulting in sin. Sin is lawlessness (1 John 3:4), the consequence of acting in a manner that is not out from faith (Romans 14:23). Until our full redemption, our struggle with the sin nature remains, for the one who ceases from sin will suffer (1 Peter 4:1). The one who acknowledges that sin is still a possibility in his life will continue to abide in the truth, but the one who denies sin will walk in darkness, deceiving only himself.