heart and soul vs sincerely

heart and soul

adv
  • With the utmost earnestness. 

noun
  • the core of a thing; the most essential or important part 

  • passion; true commitment 

sincerely

adv
  • In a sincere or earnest manner; honestly. 

  • A conventional formula for ending a letter, used when the salutation addresses the person for whom the letter is intended by his or her name. 

How often have the words heart and soul and sincerely occurred in a corpus of books? (source: Google Ngram Viewer )