You mention parents and teachers but conveniently ignore all the psychologists who do nothing but push the optimism message. They infest every area of life nowadays. It's like you haven't even read Psychology Today, which is full of it. But then, it's not like you get it right anyway. Unrealistic optimism helps a person run away from their feelings. It is a defense mechanism. It holds back a lifetime of disappointments and a lot of pain, which threatens to flood the system should you even acknowledge its presence. That's why it is not easy to shift. You think an unrealistic belief suddenly becomes realistic if we perform some action to make it seem less wrong. Not true at all. If you have violent impulses do they become normal if you act on them? If you do dangerous stuff in the belief you are being protected by some higher power, or just because you are stupid, or more likely because you have a death wish, how can you make this a healthy belief by doing anything at all? Your conclusion is so obviously wrong it is laughable. You can't get rid of a false belief by making it more believable. You have to stop running away from your feelings, feel some of the pain, and the false beliefs then wither and die of their own accord, because they are no longer needed.