I just posted a bit of a rant about being a realist. There was a book on this called "learned optimism" where mental health officials did actually test it. The results... pessimists were more factual. Optimists were factually delusional. But the thesis of the book was that you needed to learn how to be factually delusional because being a realist was too depressing. So the answer needs to be you need to be about 60% pessimist and 40% optimist.