This is one of my all time favourite definitions of mental toughness from Vince Lombardi the legendary NFL football player and coach.
“Mental Toughness is character in action”
I have paraphrased Vince because the quote was part of his longer considered opinion piece below, but to me it accurately and succinctly captures the essence of the personality trait.
“Mental toughness is many different things and rather difficult to explain. Its qualities are sacrifice and self-denial. Also, most importantly, it is combined with a perfectly disciplined will that refuses to give in. It’s a state of mind – you could call it character in action”