臥薪 がしん嘗胆 しょうたん
gashinshōtan

Noun
Suru Verb

1. going through thick and thin to attain one's objective; enduring unspeakable hardships for the sake of vengeance

Intransitive
Yojijukugo
わたくし なが あいだ臥薪 がしん嘗胆 しょうたん くるしみをなめた。
watashiwa nagai aidagashinshōtanno kurushimio nameta
I have struggled under extreme difficulties for a long time.