The phrase “good luck” needs to be retired. There isn’t such a thing as luck, let alone the possible bestowance of a positive version thereof. At least “break a leg” is evidently absurd. But even that is not actionable.

Here’s my suggestion for what we should say instead of “good luck,” which not only wishes well but also delivers specific advice: Feign confidence.

Hey Nina, just wanted to say feign confidence at your interview tomorrow! :-)

Wow, tonight is opening night for your one-man play, Tom! Feign the most confidence, my brother!