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

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
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

if one knows what's good for one

Fig. one had better do what is expected of one. You'd better be on time if you know what's good for you. If you know what's good for you, you'll call and apologize.
See also: good, if, know, one

if you know what's good for you

Fig. if you know what will be to your benefit; if you know what will keep you out of trouble. Mary: I see that Jane has put a big dent in her car. Sue: You'll keep quiet about that if you know what's good for you. Sally: My teacher told me I had better improve my spelling. Bill: If you know what's good for you, you'd better do it too.
See also: good, if, know
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

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
Farlex Partner Idioms Dictionary © Farlex 2017

if one knows what’s good for one

phr. one had better do what is expected of one. You’d better be on time if you know what’s good for you.
See also: good, if, know, one
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
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