Agreeableness is one of the 4 big personality traits as is Neurotic. There is a reason why it hasn't been selected out in human beings. People who expect bad things can prepare for bad things. The worst projects I have been on have been ones where everyone loved one another and diligently "and then" every rubbish idea. You need different outlooks to survive and flourish.

I don't know this seems a lot like work. We have sales guys who shot from the hip, are friendly with everyone, and will promise the world. And you have engineering pulling their hair out about the slow motion disaster unfolding. Together things get done.