willpower
n. uncountablen. the ability to control your own thoughts and actions so you can achieve a goal. You use it when you resist doing something you want, like eating cake, or force yourself to do something hard.
n. the capacity to exert control over one's impulses and behavior in order to achieve long-term goals. Often associated with self-discipline and the resistance of short-term temptation.
It takes a lot of willpower to quit smoking.
She relied on her willpower to finish the marathon even when her legs felt heavy and tired.
Psychologists often debate whether willpower is a finite resource that can be exhausted through use or a skill that can be strengthened over time through consistent practice.
From will + power.
Typically used as an uncountable noun; often follows verbs like 'exercise', 'strengthen', or 'test'.