There's a mentality I've adopted that I find helpful that I call "hopeful pessimism". It's the descriptive form of "Hope for the best; prepare for the worst". You expect the worst outcome, but hope you're wrong.

I think most of the devs I've enjoyed working with have similar perspectives, and often include a dark sense of humor with it. As when the hope runs out, all you're left with is something dark, and being able to laugh at the absurdity of it, to make light of it and minimize it that way, is a helpful coping mechanism, as well as one that can help bind a team together. And also helps avoid falling into despair along the way as the hits come; you can stay hopeful and focused on the desired outcome.

Maybe it depends on where in the company they are, but it seems to me that most successful founders are pretty optimistic. I know I wouldn’t want to work for a pessimist, but I agree that I wouldn’t want to be led by a completely unrealistic optimist. There needs to be some awareness of reality, but at the same time the vision and ‘reality distortion’ can help drive big successes and rally teams imho