heart and soul

heart and soul - English Dictionary

[ noun ]
■ the choicest or most essential or most vital part of some idea or experience
e.g.)
・the heart and soul of the Republican Party
→ center , centre , core , essence , gist , heart , inwardness , kernel , marrow , meat , nitty-gritty , nub , pith , substance , sum

[ adverb ]
■ with complete faith
e.g.)
・she was with him heart and soul
→ body and soul