As Paul described the “old self” in Ephesians chapter 4 he compared it to the life of the Gentiles. Unbelievers are darkened in their understanding, alienated from the life of God, hard-hearted, calloused, and greedy for impurity. Then he said:
But that is not the way you learned Christ…to put off your old self, which belongs to your former manner of life and is corrupt through deceitful desires, (Ephesians 4:20–22)
The last phrase is striking: “deceitful desires” (ESV) or “lusts of deceit” (NAS). This doesn’t mean that non-Christians want to deceive others, though that is true many times. Instead it means that sinful desires deceive the desirer. Such a person believes his own press; he’s also happens to be the author, editor, printer, and delivery boy.
The worst villains aren’t those who know their own evil, those who try on multiple black hats to see which one looks the most shady. The worst villains believe that they do no evil; they might even wear white lab coats. They allege that others misunderstand what they call “serving the greater good” or “helping mankind.” For example, Planned Parenthood advertises its abortion services as a way that they save lives.
On the individual level, and it is true of individual Christians as well, sin lies to us. Sin hides from others, but it is most dangerous because it hides from us. It’s why we must keep looking at the mirror of God’s Word. It’s also why we need to listen to others who know us and won’t accept our bull.
If people–such as your parents, disciplers, other counselors you’ve had previous reason to trust–persistently tell you that you want something that is wrong, maybe they finally cracked and now only want to make your life hell. Or maybe your desires have deceived you. The new self lives in true righteousness and holiness. Keeping sin around will keep you from seeing that clearly.