If you’d lie about where you were, that’s a clue about where you shouldn’t go.

The urge to hide something is information, and it usually arrives before your reasoning does. If the plan already includes a cover story, some part of you has worked out that it would not survive being known. That instinct is quick and reasonably accurate. Arguing it down takes effort, which is itself a sign.

Run the test before you go rather than after: would you say where you are going, plainly, to someone whose opinion you respect? If the answer makes you uneasy, you do not need a better reason to skip it. If you are already somewhere like that, leaving early is always available.