If someone spent the day with me...they would really question my intelligence
I know that what I know is nothing...
True knowledge exists in knowing that you know nothing.
I remember that from "Bill & Ted's Excellent Adventure".
Were you Bill or Ted?
I could have been either really.
Actually, it's skilled people who tend to underestimate themselves. And, while stupid or ignorant people tend to overestimate their intelligence and ability, the reverse isn't necessarily true. At the upper end of the intelligence and skill spectrums we do tend to see more cases of Imposter Syndrome, if you consider that the same thing.
Consider how much of the brain the average person uses.
That's one difference.