[mola]

As I see it, Optimism is usually unrational but drives change and Fear kills optimism.

Trust is not purely rational its emotional. Fear kills trust, making you more rational in the sense that you assume other players are rationally adversarial.

[worldsayshi]

As I see it, pessimism is as "unrational" as optimism. There's a big span of uncertainty about the future that is filled by our intentions and beliefs. If we commit to a pessimistic worldview we are likely to make some decisions that lead towards such a world. If we commit to an optimistic worldview we are likely to get exploited by bad actors.

We have to be able to juggle both realities. That is rational.

(But I think we are essentially saying the same thing here.)