To be really happy and really safe, one ought to have at least two or three hobbies, and they must all be real. It is no use starting late in life to say: "I will take an interest in this or that." Such an attempt onlyaggravates（加重，恶化）the strain of mental effort. A man may acquire great knowledge of topics unconnected with his daily work, and yet hardly get any benefit or relief. It is no use doing what you like; you have got to like what you do. Broadly speaking, human beings may be divided into three classes: those who are toiled to death, those who are worried to death, and those who are bored to death. It is no use offering the manual labourer, tired out with a hard week's sweat and effort, the chance of playing a game of football or baseball on Saturday afternoon. It is no use inviting the politician or the professional or business man, who has been working or worrying about serious things for six days, to work or worry abouttrifling（微不足道的）things at the weekend. It may also be said that rational, industrious useful human beings are divided into two classes: first, those whose work is work and whose pleasure is pleasure; and secondly, those whose work and pleasure are one. Of these the former are the majority. They have their compensations. The long hours in the office or the factory bring with them as their reward, not only the means ofsustenance（食物，生计）, but a keen appetite for pleasure even in its simplest and most modest forms. But Fortune's favoured children belong to the second class. Their life is a natural harmony. For them the working hours are never long enough. Each day is a holiday, and ordinary holidays when they come aregrudged（怀恨，吝啬）as enforced interruptions in an absorbing vocation. Yet to both classes the need of an alternative outlook, of a change of atmosphere, of a diversion of effort, is essential. Indeed, it may well be that those whose work is their pleasure are those who most need the means of banishing it at intervals from their minds.