“All these kings would do a deal better if they would put down their swords and listen to their mothers.” ~ Oleanna Tyrell, A Storm of Swords by George. R. R. Martin
It might be just me, but I think the quote has a much deeper meaning that you see at first sight. It speaks not only of kings, but generally every human on a position that turns him or her into this pompous being who believes whatever they do is the rightful thing and no one can deny them in that. Our judgement over any action is clouded by what we personally feel and often the error is done when this is perceived. A bit too late, which might not have been the case if one only took the worthy advice they were given.