I think as a human race when we take time out to actually condition ourselves to be positive or look at things in a positive light what we don't realize we're creating a false sense of security.
We're making this paradisiacal fantasy of how we want it to be in a realistic format. But what's so damaging about this process is when we put so much confidence and expectation into it, naturally we're disappointed. However we don't know how to fully accept and embrace that disappointment and it makes bitter and angry and all around upset with the world—WHY?? Because it didn't pan out the way we planned it or manifest the way we wanted.
That's why I think we have a hard time accepting failure and mistakes. That's why we say failure isn't an option, due to the selfishness of preassumed wants in life in a secured comfort zone built on desire.