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

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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