with all one's heart

• with all of one's heart

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with all one's heart

1. With much sincerity.

   I love you with all my heart.

   • 2021 September 1, Michael D. Shear, Jim Tankersley, quoting Joe Biden, “Biden Defends Afghan Pullout and Declares an End to Nation-Building”, in The New York Times‎^[1], →ISSN:

     Mr. Biden declared that he believed with “all of my heart” that he had made a wise decision.

2. (dated) Very willingly.
   • 1900, Railway Signal: Or, Lights Along the Line, volume 18, page 173:

     When Light had finished his story, his companion, Truth, said: "If you like, sister, we will turn in here and rest awhile; shall we?"
     "With all my heart," she replied, so they went in and walked round the garden.

• It is more common for of to be left out of the phrase by ellipsis.
• (with much sincerity): Usually used with verbs such as love or believe.

• all heart
• from the bottom of one's heart