optimism vs sadness

optimism

noun
  • the doctrine that this world is the best of all possible worlds 

  • a tendency to expect the best, or at least, a favourable outcome 

  • the belief that good will eventually triumph over evil 

sadness

noun
  • The state or emotion of being sad. 

  • An event in one's life that causes sadness. 

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