strength - the property of being physically or mentally strong; "fatigue sapped his strength"

trait - a distinguishing feature of your personal nature

self-command, self-possession, willpower, self-will, self-control, possession - the trait of resolutely controlling your own behavior

bullheadedness, pigheadedness, self-will, stubbornness, obstinacy, obstinance - resolute adherence to your own ideas or desires

single-mindedness - characterized by one unified purpose

adamance, obduracy, unyieldingness - resoluteness by virtue of being unyielding and inflexible

decisiveness, decision - the trait of resoluteness as evidenced by firmness of character or purpose; "a man of unusual decisiveness"

determination, purpose - the quality of being determined to do or achieve something; "his determination showed in his every movement"; "he is a man of purpose"

steadfastness - steadfast resolution

hardness - the property of being rigid and resistant to pressure; not easily scratched; measured on Mohs scale

immovability, immovableness - no capable of being moved or rearranged

granite - something having the quality of granite (unyielding firmness); "a man of granite"

sureness - the quality of being steady and unfailing; "sureness of hand"

stability, stableness - the quality or attribute of being firm and steadfast