My third maxim was to endeavor always to conquer myself rather than fortune, and change my desires rather than the order of the world, and in general to accustom myself to the persuasion that except our own thoughts, there is nothing absolutely in our power; [...] since our will naturally seeks those objects alone which the understanding represents as in some way possible of attainment, it is plain that if we consider all external goods as equally beyond our power, we shall no more regret the absence of such goods as seem due to our birth [...] than our not possessing the kingdoms of China or Mexico [...]. But I confess there is need of prolonged discipline and frequently repeated meditation to accustom the mind to view all objects in this light [...].

—René Descartes, Discourse on Method.