Of all of the sins that I see otherwise brilliant people commit in the world of art and commerce, it is the sin of hubris. Of arrogance, of pride, of self importance. We know it all, we've seen it all and there is nothing at all new that can be shown to us.
Conversely, I have had the opportunity to have at boss who, as a veteran of nearly twenty years in her position, found a way to always be optimistic and open to ideas. She would actively listen, develop them, ask other's opinions, and then attempt to execute. She never complained, she never said anything disparaging. She just worked.
However, I once asked her "I'm sure that you've seen most of these initiatives proposed and attempted before, right?" She answered by saying something like "Of course. However, I'm always learning to execute things on a higher level, and within reason, maybe now will be the time that it works."
I know that this doesn't work for everyone or in every position. It also isn't a call for foolishly repeating things over and over that don't work. That's not the point.
The point here is that her attitude, her willingness to keep the beginner's mind, to have an empty cup, made her infinitely better at her job and as a leader. She took her ego out of it and made it all about pure service. She was committed to constantly growing and developing, even after twenty years. Call it what you will, but to me, that's what excellence looks like...