open one's heart vs speak one's mind

open one's heart

verb
  • (figuratively) To speak honestly and vulnerably about one's feelings. 

  • To show great compassion. 

speak one's mind

verb
  • To state one's thoughts or opinions honestly or frankly. 

How often have the words open one's heart and speak one's mind occurred in a corpus of books? (source: Google Ngram Viewer )