Don't show that you're upset, in the face of adversity be self-reliant, remain calm.
Just before starting to cry the lips tend to tremble. In which case, why does this expression refer only to the top lip? One theory is that, in the 19th century, most men had moustaches which would have made a quivering top lip more noticeable than the bottom.
Similar in meaning to "chin up", "keep a stiff upper lip" would see seem to be the epitome of Englishness (e.g. The Jeeves novel, Stiff Upper Lip by P. G. Wodehouse). However, apparently it originates in the USA, having been traced back as far as 1815.
"What's the use of boohooin'.... keep a stiff upper lip no bones broke -- don't I know?"
- Down Easters (1833) by John Neal.
British Parliament asks Amazon to clarify why it pays $9 million in income tax on $23 billion of UK sales.(May 20 2013) Amazon will be called back to give further evidence to members of the British Parliament "to clarify how its activities in the U.K. justify its low corporate...