Voltaire's "Candide" was published in 1759. The book is sometimes called The Optimist or Optimism. You may know that various authorities as well as research studies point toward an optimistic life as a healthy one.
https://www.gutenberg.org/files/19942/19942-h/19942-h.htm
The link goes to the Gutenberg Project, a collection of files that can be read online or downloaded.
Candide is taught by a learned man that "all is for the best in this best of all possible worlds." Many people have yucky experiences of death, destruction, deception and destitution that makes them feel that idea is clearly wrong, wrong and also wrong. Meanwhile, with drugs, including the famous alcohol, and dance and music and the company of the right sexual companions, people can sometimes learn to stay in an upbeat mode steadily, keeping themselves convinced of the glory and fun of life despite all. I have a book (don't I always?) called "Get High Now - without drugs" by James Nestor, who is also the author of a more recent popular book, Breath.
A good recent book about overdoing optimism is "Bright-sided" by Barbara Ehrenreich. It is a good read, I think, and shows some good examples of organizations and businesses that have really over-bought into "the power of positive thinking", way past the boundary of good sense and judgment.
With practice and commitment, a person can train himself to be steadily positive, even when such thinking is inappropriate. The right emergency, the right misbehavior and it makes sense not to accept the event as wonderful. It is possible that the consequences will eventually include genuinely good things but within reasonable judgment, there seem to be times and occasions that call for negative thinking.
