Earlier quoted context omitted.
Keep in mind you can be disappointed in more than one way. Either you tried the impossible with an optimistic mindset and failed anyway, or you failed at something doable because you took pessimistic choices. It's not actually obvious which category this is in.
Yes, but the optimistic mindset would probably have a better outcome than the latter regardless if they failed to meet their original expectations or not.
It seems we should need objective data to filter through the bias.