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
Farlex Dictionary of Idioms.

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
See also:
  • come to no good
  • do no good
  • (one) (has) never had it so good
  • for good measure
  • be as good as new
  • do (one) a/the world of good
  • as good as it gets
  • as good as new
  • (as) good as new
  • expectation
References in classic literature
"You'll sit right there, if you know what's good for you. Now be good and mind what I say.
The Valley of the Moon
"You keep off if you know what's good for you!" he called out suddenly, as though he had made up his mind as to who and what we were.
Tales of the Fish Patrol
"Look here, Paul, you'll keep out of this if you know what's good for you."
Moon Face and Other Stories
Try not to to start an argument today, if you know what's good for you. However, it is time to stride confidently forward.
YOUR HOROSCOPE WITH
Our response has been an unvarying 'Don't give in if you know what's good for you.'
Lubricating business transactions
If you know what's good for you, you will make yourself free for him even if you have a pressing appointment.
Handymen are never at hand
stay away from that moon door if you know what's good for you.
Now meet the Great Scousers of Westeros
If you know what's good for you, you'll leave it there."
POLICE What are you doing with that young girl, Jimmy? JIMMY SAVILE Waiting 'til midnight.. it's her 16th birthday; Officer found DJ in Rolls with teen
I did not bother with the waste of time meetings because of the attitude of 'we know what's good for you'.
My free think tank; Your say
Now you know what's good for you, it's also essential you don't let bad habits get in the way.
SMALL STEPS CAN MAKE A HUGE DIFFERENCE
YOU KNOW WHAT'S GOOD FOR YOU, YOUIL VOTE FOR THE SWEET AND SOVR SPAM CHILL ...
Lying in state
DON'T mess with the dame if you know what's good for you.
ALL AC CCTION HELEN Dame loves; Dame loves the rough and tumble of new film
I'm not writing here to force a new version Christ on you O reader but if you know what's good for you you will take the first chance at knowing Him that you can get."
To the Church of the West Scattered Throughout the World
London, Dec 27 (ANI): When Oprah Winfrey and Kate Moss espouse "detox" regimes or, when Sharon and Kelly Osbourne say that the Pill can cause cancer, don't take them too seriously if you know what's good for you, say scientists and doctors.
Celeb health tips 'more of quackery than scientific reality'
"Things are distorted with the booze haze and you don't know what's good for you. I plan to stay away from it and have replaced it with a new vice - writing.
GENE GENIUS; EXCLUSIVE: Carl's movie debut as rocker Vincent