keep a civil tongue in your head

US /kiːp ə ˈsɪv.əl tʌŋ ɪn jʊər hɛd/
UK /kiːp ə ˈsɪv.əl tʌŋ ɪn jʊər hɛd/
"keep a civil tongue in your head" picture
1.

丁寧な言葉遣いをする, 口を慎む

to speak politely and avoid rude or offensive language

:
You need to keep a civil tongue in your head when talking to your elders.
年長者と話すときは、丁寧な言葉遣いをしなさい
Even when angry, try to keep a civil tongue in your head.
怒っていても、丁寧な言葉遣いを心がけなさい