If you want to be more successful — at anything — than you are right now, you need to know yourself and your skills. And when you fall short of your goals, you need to know why. This should be no problem; after all, who knows you better than you do?
And yet your own ratings of your personality traits — for instance, how open-minded, conscientious, or impulsive you are — correlate with the impressions of other people (who know you well) at around .40. In other words, how you see yourself and how other people see you are only very modestly correlated.
In his fascinating book Strangers to Ourselves, psychologist Timothy Wilson summarizes decades of research on what he calls our adaptive unconscious, showing us just how much of what we do during every moment of every day — what we think, how we feel, the goals we pursue and the actions we take — is happening below our conscious awareness. Some of it we can notice if we engage in a little self-reflection, but much of it we simply cannot — it’s not directly accessible to us at all.
You certainly don’t need to take my diagnostic to figure out how where your weaknesses lie. The point is that you will absolutely need feedback — the kind you can trust — because trying to figure it all out on your own is close to impossible. Relying on our intuitions alone for self-knowledge is dangerous, because thanks to the nature of the adaptive unconscious, they are often no more accurate than a shot in the dark.