How would I know how much I don't know I know? And if I don't know something about myself, and nobody else does either, does it even exist?
Because knowing that there are things you don't know is important, and always be aware that there are things you don't even know you don't know... at least yet. For example... I know that I am not a doctor and do not know medicine. Which is different than not even knowing there are doctors.
There are things you do not know about yourself that others don't know either... this could be an as-yet-untapped strength or weakness that has yet to display itself to either you, or others observing you.