backbone bottom chutzpah decisiveness endurance energy force fortitude grit guts gutsiness guttiness hardiness heart heart of oak heartiness lustihood lustiness mettle might mightiness moxie nerve obstinacy pith pluck potency power powerfulness robustness ruggedness sand spirit spunk stalwartness stamina staying power sticking power stout heart stoutness strength strength of will sturdiness toughness vigor vigorousness vitality