Well, that would be fair, except I've stated no preference for pessimism:)) In my view it is just as important as Optimism. Two sides of the same coin.
Edit: and the current situation demonstrates that, in fact, reality itself can be horrible enough for the Pessimists to be right:))
Sure, if you want to neglect the value of trying to picture a better and a worse.
Honestly, you seem to have a problem with Pessimism itself by default, in which case there's nothing more I can say here.
And, to answer your question, how does one learn if not by first being wrong about things?