cautionary
Serving as a warning to help you avoid problems.
Cautionary means serving as a warning about what not to do or what could go wrong. A cautionary tale is a story that shows the consequences of making bad choices, like the fable of the boy who cried wolf, warning readers about what happens when you lie too often.
When something is cautionary, it's meant to make you think twice before acting. A teacher might share a cautionary example about a student who waited until the last minute to start a big project and ended up doing poorly. Your parents might offer cautionary advice about riding your bike without a helmet, explaining what could happen if you fall.
A cautionary note doesn't forbid you from doing something; it simply alerts you to the risks so you can make a wiser choice. Road signs are cautionary when they warn of sharp curves ahead. A friend's cautionary words might remind you to save your video game progress before fighting that difficult boss. Cautionary messages help us learn from others' mistakes instead of making all those mistakes ourselves.