One lie needs a second lie to stand up. Then it needs a whole crew.

A lie is a structure that requires maintenance. It has to stay consistent with everything else you say, so each new conversation risks it and each risk gets patched with another piece, and the whole construction grows without you deciding to grow it. Most people are not caught by a dramatic revelation. They are worn down by the upkeep.

If one is currently standing, the cheapest moment to take it down is now, and it only gets more expensive. Tell the one person it most affects, plainly, with no long preamble.