IPA: /ˈwɪlˌpaʊər/
KK: /ˈwɪlˌpaʊər/
The ability to control your thoughts and actions in order to achieve something you want, especially when it is difficult.
She showed great willpower by sticking to her diet even during the holidays.
Willpower → It is formed from "will" (from Old English "willan", meaning to wish or desire) and "power" (from Old French "poeir", meaning to be able). The word "willpower" refers to the ability to control one's wishes or desires to achieve a goal.
Think of your 'desire' ('will') combined with your 'ability' ('power') to control that desire — that's what willpower means.