Charity Navigator CEO Ken Berger can't say enough about staying humble.
"Whatever your position or salary, never think you are smarter, better, or in some way the keeper of unique knowledge and expertise; that is the way to ultimately isolate yourself and it will lead you on a path of career destruction and/or to a miserable and empty existence. People may tell you how brilliant you are and compliment you in all kinds of ways as you become a 'big boss man,' but do not ever think of yourself as superior to others. Anyone who thinks they are the smartest person in an organization is usually the real idiot!"
Source: LinkedIn Author Ken Berger