Lying to yourself is the most comfortable lie there is. It never argues back.

Every other untruth meets resistance eventually, because someone else holds a different set of facts. The one you tell yourself has no opposition at all; it is agreed to instantly and never raised again. That absence of friction is what makes it comfortable, and what lets it sit undisturbed for years.

Say the thing you believe out loud to one person who will not simply agree. Outside air is the only reliable test, and a single honest listener does what a hundred private reconsiderations will not.