self-assurance vs serenity

self-assurance

noun
  • The state or quality of being confident in oneself. 

serenity

noun
  • The state of being serene; calmness; peacefulness. 

  • A lack of agitation or disturbance. 

  • A title given to a reigning prince or similar dignitary. 

How often have the words self-assurance and serenity occurred in a corpus of books? (source: Google Ngram Viewer )