be on (one's) mettle

be on (one's) mettle

To be determined to succeed and thus prove one's worth, often in a difficult or unpleasant situation. I know my employees think I'm too young to be their supervisor, so I have to be on my mettle every day at the office.
See also: mettle, on
Farlex Dictionary of Idioms.

be on your mettle

be ready or forced to prove your ability to cope well with a demanding situation.
See also: mettle, on
Farlex Partner Idioms Dictionary

be on, show, prove, etc. your ˈmettle

be prepared to do the best work you can or perform as well as you can in a particular situation: When the boss comes round, I want you all to show your mettle. He’ll have to be on his mettle if he wants to win the next race.
Mettle is the ability and determination to do something successfully in spite of difficult conditions.
See also: mettle
Farlex Partner Idioms Dictionary
See also:
  • like pulling teeth
  • come to a bad end
  • come to a bad/sticky end
  • go from bad to worse
  • from bad to worse
  • fall out with (someone) about (something)
  • get (someone) out of (something)
  • gut-wrenching
  • get out of
  • get (oneself) out of (something)