My third maxim was to endeavour always to conquer myself rather than fortune, and to change my desires rather than the order of the world, and in general to bring myself to believe that there is nothing wholly in our power except our thoughts. And I believe that herein lay the secret of those philosophers who, in the days of old, could withdraw from the domination of fortune and, despite pain and poverty, challenge the felicity of their gods.

—René Descartes, Discourse on Method.