noun
one's whole heart; with all one's heart
Refers to putting one's entire heart or soul into something. Often used in expressions like 全心を込めて or 全心で.
彼は全心を込めてその曲を演奏した。
He performed the piece with all his heart.
全心で取り組めば、きっと成功する。
If you tackle it with your whole heart, you will surely succeed.