I'm going to add some that may have been missed:

Know how to listen.
Know how to express your own feelings and be aware of others'.
Become appreciative of things like subtlety and balance.
Learn how to avoid extremes and practice moderation.
Know how to control your temper...and your tongue.
Know how to take advice when you need to.
Know when is the time to change your mind about something you thought you had your mind made up about.
Know how to be flexible....

How many presidents have managed all of the above? ;-)