One small lie turns every future sentence you say into a maybe.

Trust works like a default setting. Once somebody catches you in something small and untrue, they stop taking your statements at face value and start assessing each one, and that assessment never fully switches off. You have not just lost that sentence, you have added a question mark to all the future ones, including the true and important ones. Rebuilding it is slow precisely because it happens silently.

If you have told one, correct it yourself before anyone finds out. Say you got that wrong and give the real version. It costs one awkward minute now.