courage vs strength of mind

courage

noun
  • The ability to overcome one's fear, do or live things which one finds frightening. 

  • The ability to maintain one's will or intent despite either the experience of fear, frailty, or frustration; or the occurrence of adversity, difficulty, defeat or reversal. Moral fortitude. 

  • The quality of being confident, not afraid or easily intimidated, but without being incautious or inconsiderate. 

strength of mind

How often have the words courage and strength of mind occurred in a corpus of books? (source: Google Ngram Viewer )