Si ves las barbas de tu vecino arder, pon  las tuyas en remojo.

Translation: If you see your neighbor’s beard catch on fire, you should soak your own, which means take precautions when bad things happen to someone else in a similar situation.

Example: Paul flunked his physics test, so I better study extra hard for mine–after all, if you see your neighbor’s beard catch on fire, soak your own…