| self-will(discipline, willpower, self-discipline) |
| seriousness(noun, resolve, firmness, willpower) |
| single-mindedness(noun, resolve, determination, purpose, fortitude) |
| sobriety(discipline, willpower, self-discipline) |
| soul(noun, character, strength, courage, will) |
| sparkle(noun, character, strength, courage, will) |
| spine(noun, resolve, firmness, purpose, fortitude) |
| spirit(character, strength, courage, will, guts) |
| spunk(noun, character, strength, resolve, courage) |
| stability(discipline, willpower, self-discipline) |
| steadfastness(noun, resolve, purpose, fortitude, grit) |
| stiff upper lip(noun, expression, idiom, resolve, purpose) |
| stoicism(discipline, willpower, self-discipline) |
| stoutheartedness(noun, character, strength, courage, will) |
| strength of character(noun, expression, idiom, resolve, discipline) |
| strength of will(noun, expression, idiom, resolve, restraint) |
| stubbornness(noun, resolve, firmness, purpose, fortitude) |
| substance(noun, character, strength, courage, will) |
| surety(noun, resolve, firmness, willpower) |
| temper(noun, character, strength, courage, will) |