know what's good for you

if (one) knows what's good for (one)

If one wants to avoid trouble (one will do or avoid a certain thing). Oh, you'll be on time for the meeting, if you know what's good for you. If he knows what's good for him, he'll stop calling me that.See also: good, if, know

know what’s ˈgood for you

know what is necessary for you to do to be successful, etc.; know how to avoid trouble: If you know what’s good for you, young man, you’ll talk to nobody about what you’ve seen here tonight.See also: good, know