Excerpt from The Art of Worldly Wisdom by Baltasar Gracián.

lxix Do not give way to every common Impulse.

He is a great man who never allows himself to be influenced by the impressions of others. Self-reflection is the school of wisdom. To know one's disposition and to allow for it, even going to the other extreme so as to find the juste milieu between nature and art. Self-knowledge is the beginning of self-improvement. There be some whose humours are so monstrous that they are always under the influence of one or other of them, and put them in place of their real inclinations. They are torn asunder by such disharmony and get involved in contradictory obligations. Such excesses not only destroy firmness of will; all power of judgment gets lost, desire and knowledge pulling in opposite directions.