All impersonal interests, apart from their importance as relaxation, have various other uses. To begin with, they help a man to retain his sense of proportion. It is very easy to become so absorbed in our own pursuits, our own circle, our own type of work, that we forget how small a part this is of the total of human activity and how many things in the world are entirely unaffected by what we do.
Source: The Conquest of Happiness, 1930, chap. 15：Impersonal interests