Initial thoughts- Endurance sports, contact sports, medical profession - triaging people in a ER when they al need help smut require a form of mental toughness, I'm sure there are others.
I think someone who has mental toughness developed in another area has a bit of a head start in the fighting / defensive realm.
As we used to say when I taught at my agency's academy, we can teach you to fight, we can teach you to shoot but we can't teach Heart.