The better ambitions have to do with the development of character and ability, rather than status and power. The status you can lose. You carry character with you wherever you go, and it allows you to prevail against adversity.
Dare, instead, to be dangerous. Dare to be truthful. Dare to articulate yourself, and express (or at least become aware of) what would really justify your life.
Anyone who was out to change the world by changing others was to be regarded with suspicion. The temptations of such a position were too great to be resisted.
