The Wisdom of Life is a practical essay on happiness, what Schopenhauer calls eudaemonology: the art of ordering one's life to obtain the greatest possible well-being. He begins by dividing the differences in human fortune into three classes: what a man is, what a man has, and how a man stands in the estimation of others. The whole essay weighs these against one another.
The first class, personality, is treated as decisive. Health, strength, temperament, moral character, and intelligence belong to a person himself and accompany him everywhere. Because every event is colored by the mind that meets it, the same circumstances affect no two people alike, and each lives in a world shaped chiefly by the way he looks at it. What a man is in himself is therefore the immediate and lasting source of his happiness, while everything external acts only indirectly.
Among personal goods, Schopenhauer ranks health and cheerfulness highest. A genial flow of good spirits is its own reward and the very coin of happiness, paid in the present moment. Nothing promotes it so little as riches or so much as health, so he counsels avoiding excess and maintaining the body. He then identifies pain and boredom as the two foes of happiness: the needy struggle with pain, the comfortable with boredom, and life oscillates between the two poles.
The remedy he proposes is inward wealth, the activity and resources of a cultivated mind. A dull person, easily bored, chases excitement and society to escape an inner vacuity; a person of intellect finds inexhaustible material in his own thoughts and so stands beyond the reach of boredom. From this follows his praise of solitude and independence: the more a man has in himself, the less he wants from others, and the wiser he is, the more he will choose a quiet, modest life over the company of the crowd.
The shorter treatments of property and position complete the argument. Wealth, Schopenhauer says, is relative to one's claims and never absolutely satisfying; like sea-water, it leaves one thirstier. Position, the regard of others, has no direct existence for us and matters only as it affects how we are treated. Reputation, pride, rank, honor, and fame are examined and largely deflated, returning the reader to the essay's governing claim that happiness is built from within.