Daily Chinese Idiom Guessing Game
To be perfectly willing to do something; to do something of one's own free will.
心里完全愿意，没有一点勉强。多指自愿做出某种牺牲。
宋·王明清《摭青杂说·项四郎》此事儿甘心情愿也。”
She willingly stayed late to help her colleague finish the project.