Maturity, coolness and steadiness are some of the qualities cabin crew must possess. The job of a flight attendant is not just about passenger comfort and welfare but it's more than that.
When a passenger buys a ticket, he expects the airline to fly him safely to his destination. This is the most important thing in a passenger's mind. Comfort and food etc are secondary.
There will be air disasters, albeit few. Less than 10% air accidents were unplanned. 90% were premeditated. It means the would be crashes were known to the technical and cabin crew eg. engine failures, intractable undercarriages etc.
The crew have to prepare the aircrafts and passengers for such situations. They are trained to handle such situations. The priority for the crew is to save as many lives as possible would there be such scenarios.
A B707 belonging to MSA, the predecessor of SIA had a major mechanical problem that would cause the plane to crash on landing. The year was 1969.
On hearing the news, a stewardess on that flight became hysterical and yelled loudly that she didn't want to die. Passengers heard the commotion and they too panic. The stewardess's frightening cry demoralised the whole set of crew.
Fortunately the quick witted chief steward restrained the stewardess and stopped her from crying loudly.
In the end,the plane did not crash landed due to the skillful pilots who manoeuvred the it out of trouble.
From that incidence, the airline decided they should not recruit crew who may be the panicky type.
The airline also look for "steadiness" in its cabin crew not just to save lives should there be an air crash but to look after the safety of the aircrafts and the passengers from any harm arising from terrorism.
These days, cabin crew are also trained in the art of self defence and some form of martial arts.
On some airlines, the chief pursers must be at least a black belt holder of Karate or Tae kwon Do. There are a few airlines whose chief pursers are licensed to carry guns on the flight.