He posits:
- Definite pessimists have a concrete negative potential future in mind and often work to subjugate it
- Indefinite pessimists have a vague "the future looks negative" and don't act on concrete plans to improve it
- Definite optimists have a concrete positive potential future in mind and often work to make it a reality
- Indefinite optimists often have a vague "everything will be fine" mindset and rely on others to make that a reality
On a general sense, I'd wager that both optimists and negatives are a good idea to have at the collective level, as both are driven by similar but different motivations. I'd say it's the definite subsets of each group that are "realistic" and "useful" as it pertains to the future, rather than either larger group as a whole.
That's impossible for anyone in the world.
A pessimist and an optimist will probably consider various interpretations as realistic, yet neither will see the world "as it is".
Even just the idea of the world as something that can be seen, thought of, considered, described etc. is squeezing it through a very human-shaped filter, and what you get out of the other end is always more about us than about the world.
It's a principle among the Hasidim, too. The followers of Rabbi Nachman of Breslov believe that we should feel commanded to be happy at all times:
A pessimist cynic will say "that's just the way it is" for example.
Additionally pessimism and optimism are mainly about thinking about the future rather than objective state of now.
Perhaps it's stocism that's a more fitting alternative.
'Be happy. Or else.'
https://www.youtube.com/watch?v=eVM1nUmDHHc (Ren & Stimpy Happy Happy Joy Joy Song)