act your age

act (one's) age

To behave in accordance with one's expected level of maturity. Really, John, act your age a little. You're like a child sometimes! I'm glad that Sarah is so committed to her studies, but sometimes I wish she would act her age and go out with her friends a bit.
See also: act, age
Farlex Dictionary of Idioms.

act your age

If you tell someone to act their age, you are telling them to behave in a way that is suitable for their age, because they are behaving in a childish way. One patient complained that the nurse had told her: `Act your age and pull yourself together.' Note: This expression is used to express disapproval of someone's behaviour.
See also: act, age
Collins COBUILD Idioms Dictionary, 3rd ed.

act your age

behave in a manner appropriate to your age and not to someone much younger.
See also: act, age
Farlex Partner Idioms Dictionary

ˌact/ˌbe your ˈage

(informal) (often used as a command) stop behaving like a child: You’re behaving like a couple of kids. Act your age!
See also: act, age
Farlex Partner Idioms Dictionary

act your age

Don’t be childish or act foolish. This admonition appears to date from the 1920s. “Be your age” is the caption of a 1925 New Yorker cartoon; “act your age” appears in a 1932 issue of American Speech, a journal that chronicles current usage.
See also: act, age
The Dictionary of Clichés by Christine Ammer
See also:
  • act (one's) age
  • act one's age
  • Act your age!
  • act/be your age
  • courage of one's convictions, have the
  • have the courage of (one's) convictions
  • have the courage of convictions
  • have the courage of your convictions
  • have/lack the courage of your convictions
  • lack the courage of (one's) convictions
References in periodicals archive
Several members of 3rd Stage also go to (Don't) Act Your Age, LBT's drama group for the over- 50s.
Come on over-50s, it's for you; Over 50s
When it comes to choosing fiction, you don't have to act your age. Some of the most moving, courageous, and innovative new writing is in gay-themed novels for young adults.
Youth fiction grows up: for the gifted crop of writers telling stories for and about gay youths, the old cliches are so-o-o over
Act Your Age! A Cultural Construction of Adolescence.
Lesko, Nancy. Act Your Age! A Cultural Construction of Adolescence
If you do not act your age others will perceive you differently; if you act your age then do not be surprised how others perceive you.
Don't think old - think grey power
All I can say is grow up and act your age. However, if you really can't control your cruel side, then at least save it for adults - ones that have the capacity to fight back.
Pick on an adult instead; YourSay
"You're a sad old bag who can't act your age", stormed Scott's step-sister, Kelly.
LAST NIGHT'S VIEW
Time she took some sage advice from that great Brits per former Prince, who once sang: "Act your age, not your shoe size, honey."
OLD BIRD'S GOT A FOWL MOUTH