I have seen a lot more problems come from an excess of optimism, than an dearth of it. You should not be so optimistic that you don't think about how to roll b

I have seen a lot more problems come from an excess of optimism, than an dearth of it. You should not be so optimistic that you don't think about how to roll back changes if they turn out to be a bad idea, for example. Backups and rollback plans and code reviews and etc. are all fundamentally pessimistic. An excess of optimism can lead to no plan B. Every startup pivot relied upon NOT having so much optimism that you will not believe a pivot is required. Not to say that optimism is all bad, but it's not all good either, and in the U.S. corporate world I see a lot more problems from an excess of optimism than from the reverse.