海誓山盟鬼才信鬼才信海誓山盟
[hăi shì shān méng guĭ cái xìn guĭ cái xìn hăi shì shān méng]
Literally translating to 'vows as firm as mountains and seas—who would believe such vows', this indicates distrust towards overly dramatic or romanticized promises that seem hard to come true.