presence of mind vs serenity

presence of mind

noun
  • Focused alertness, quick-thinking resourcefulness, stability of thought and feeling, or good sense, especially in spite of circumstances which are distracting, stressful, or otherwise challenging. 

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 presence of mind and serenity occurred in a corpus of books? (source: Google Ngram Viewer )