muster up vs take heart

muster up

verb
  • Look within oneself to summon a particular positive quality, such as strength, energy or courage. 

take heart

verb
  • To be courageous; to regain one's courage. 

intj
  • Used when encouraging someone to bear or take up a difficult situation. 

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