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.
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]