it's about 99% mental
Toughness is almost all mental. Good attitude, perseverance, willingness to try new things and give it your best shot. This only supplemented by physical toughness: endurance, strength, ability to take a hit, etc. Probably the toughest from either gender that I ever met was at the Gloucester beach weekend over the summer. Athena from Texas practices combat ki, and she took a couple \"medium\" punches to the throat. She is obviously extremely physically tough, but it's mostly becuase she knows how to keep cool in a bad situation, and has total control over muscle groups most people forget they even have.
Still in Progress...maybe someday I'll get to a good place.