An expert is a man who has made all the mistakes, which can be made, in a very narrow field.
— Neils Bohr

An expert is one who knows more and more about less and less.
Nicholas Murray Butler expertise quote

Never become so much of an expert that you stop gaining expertise. View life as a continuous learning experience.
— Denis Waitley

You must continue to gain expertise, but avoid thinking like an expert.
— Denis Waitley

Make three correct guesses consecutively and you will establish a reputation as an expert.
— expertise quotation by Laurence J. Peter