1
general::
Phrase(s): Keep a stiff upper lip.
Prov. Act as though you are not upset.; Do not let unpleasant things upset you. (English people are stereotypically supposed to be very good at keeping a stiff upper lip.) • Even though he was only three years old, Jonathan kept a stiff upper lip the whole time he was in the hospital recovering from his surgery. • Jill: Sometimes this job frustrates me so much I could just break down in tears. Jane: Keep a stiff upper lip. Things are bound to improve.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Show courage in the face of pain or adversity. For example, I know you're upset about losing the game, but keep a stiff upper lip. This expression presumably alludes to the trembling lips that precede bursting into tears. [Early 1800s]
American Heritage Idioms