Say, something happens that you didn't expect. A classic perfectionistic thought pops into your mind: "This wasn't supposed to happen!" You didn't suppose it would happen but it did, didn't it? Who's wrong here: reality or your theory about reality?
You see, we constantly match our ambitious minds against the bewildering complexity of reality, testing our assumptions, suppositions, hypotheses and theories. When as a perfectionist you find yourself in a situation where the reality doesn't match your theory, you conclude that it is the reality that is wrong, not your theory.
Reality is never wrong. As Alexander Pope astutely observed, whatever is, is right. Our knowledge of reality - individual and collective - is an open-ended model in constant need of revision.
So, here's a humility check for you to try. Whenever something goes "wrong," i.e. not the way you supposed it to go, choose to shift from frustration to awe. Marvel at the bewildering, nuanced, multifaceted complexity of what is. Say to yourself: "Wow!"
Instead of chastising yourself, allow recognize that you made the best prediction you could about how reality would be, but you have obviously and understandably underestimated the mind-boggling complexity of it all; perhaps, you weren't aware of all the variables involved; perhaps, you didn't have enough computational sophistication to extrapolate the most likely trajectory of reality. How could have you known what you didn't know? If you had known what you didn't know you predictions would have been different! It's time to factor in the new data, to update your assumptions, to revise your model, and to say "Wow!"