assurance audacity brashness bulldog courage cohesiveness decisiveness durability endurance energy force fortitude gameness gaminess grittiness guts gutsiness haleness hardihood hardness heartiness infrangibility intestinal fortitude lastingness leatherlikeness longevity lustihood lustiness mettlesomeness might mightiness nerve nerviness obstinacy pertinaciousness pertinacity pluckiness potency power powerfulness resistance resoluteness resolution robustness ropiness ruggedness spunkiness stalwartness stamina staying power sticking power stiffness stoutness strength strength of will stringiness stubbornness sturdiness tenaciousness tenacity toughness unbreakability unbreakableness vigor vigorousness viscidity vitality