Bonjour. I think in many cases we have to choose one of the translations dependeng on the sentence or situation. Examples from some webpages: I've already lost my willpower. (気力 きりょく) You have a strong willpower. (意志 いし) I'm on a diet but when I saw cake, I have no willpower. (自制心 じせいしん) If you have example(s), could you show it/them to us? I hope this was helpful.

"willpower": Comment ça va pour les mots de «決心(けっしん)» [comme un substantif] et «決断(けつだん)する» [comme un verbe] ? === 良い一日をお過ごし下さい。／Je te souhaite une bonne journée.