Optimists don't understand, or want to understand people they deem pessimists. For them being always wishful, happy, curious, whatever they claim as "optimistic" is only way to live, and every other view is wrong and needs to be fixed.
I've always been pessimistic. That however doesn't mean I'd give up just because "it's going to fail anyway, so why bother". I expect things to bad, so I make sure to do best I can - while being ready for getting kicked down. Negative kicks are far easier to handle. Positive events seem even more unreal and good, than if you had expected it.
I'll give real life example: theory test in school. I usually don't bother reading for them. Go, and do best you can. Be pessimistic of the results; be fine and accept it if the score is low as you expected, be surprised and genuinely happy if score is higher than you expected.
How is that something that needs 'fixing'?
Frankly I'm not sure if I even fall in category "pessimist"; optimist I clearly am not, rather something between pessimist and realist. They need to invent new isms between each..
I'll always love quote of Lewton in Discworld Noir: "Pessimism is a term used by optimists to attempt to discredit those who see the world as it really is."
Although another quote I always find amusing is from Moonspell's Heartshaped Abyss: "Never resist; the lifelong pessimist; he is the leader; and not the enemy".
Doubt I'd make good leader. Although I didn't get much negative feedback from my last attempt in it with 'coordinator' for tutors in our school, something I requested while being BP's happyhappy moodswing. Ask right questions, make sure your flock is prepared for things to go worse than they optimisticly expect, let them run free while watching from the shadows how they'll do, and if there's something you need step out for - either for making their wacky plans slow down, or having to negotiate their plans with next higher step in the system.
I don't know, does that sound like good leading strategy?