Some things, once done, cannot be undone.

Somebody told a lie, and somebody believed it. Now look what it has done.

Lies, once told, cannot be untold. The liar might regret that he has told a lie, because at the point of lying, he never expected that he'd be reaping any sort of consequences from the lie. He told the lie simply to get back at someone.

The only people who can be sure he's lying are the truly discerning ones. They'll know that the liar's lie sounds not too unbelievable, but too believable, to be true.

But now the liar regrets having told a lie, because he's suffering for it. Yet he's come so far and cannot untell his lie. His pants are on fire.