stiff upper lip

صورت خود را با سیلی سرخ نگه داشتن

کنترل احساسات و آرام ماندن در شرایط سخت

منظور آرام ماندن و نشان ندادن احساس ترس در هنگام رویارویی با مشکلات
(چون در شرایط ترس لب بالا شروع به لرزیدن می کند)
The phrase is most commonly heard as part of the idiom "keep a stiff upper lip", and has traditionally been used to describe an attribute of British people in remaining resolute and unemotional when faced with adversity.
A sign of weakness is trembling of the upper lip, hence the saying keep a stiff upper lip. When a person's upper lip begins to tremble, it is one of the first signs that the person is scared or shaken by experiencing deep emotion.