The forms of zest are innumerable. Sherlock Holmes, it may be remembered, picked up a hat which he happened to find lying in the street. After looking at it for a moment he remarked that its owner had come down in the world as the result of drink and that his wife was no longer so fond of him as she used to be.
Life could never be boring to a man to whom casual objects offered such a wealth of interest. Think of the different things that may be noticed in the course of a country walk. One man may be interested in the birds, another in the vegetation, another in the geology, another in the agriculture, and so on. Any one of these things is interesting if it interests you, and, other things being equal, the man who is interested in any one of them is better adapted to the world than the man who is not interested.
-- Bertrand Russell, The Conquest of Happiness, p. 95
