The feeling of chagrin or frustration after a failure or loss; often used in expressions like 'use the frustration as motivation'.
試合に負けた悔しさを胸に、彼は毎日練習した。
Bearing the frustration of losing the match in his heart, he practiced every day.
合格できなかった悔しさが、次の挑戦の原動力になった。
The bitterness of not passing became the driving force for the next challenge.
悔しさのあまり涙が止まらなかった。
She couldn't stop crying from sheer frustration.