(Some of the following is taken from Why I Like Stamp Collecting by Ayn Rand)
Its 7 in the evening and you have just returned from many hours of shopping or at the office. Your spouse is plopped down on the couch watching TV. You hear "God! I need a vacation!" You think "From what? You don't work. What do you need a vacation from?"
Hobbies and relaxation serve the same function as a vacation; they are ways to refuel your body and mind. But refuel them from what? A couch potato, an office goof-off or a playboy do not spend their days burning any fuel, mental or physical. They have done nothing to take a vacation from. A hobby is an adjunct of, not a substitute for, a career. If one makes a hobby a substitute for productive work, it becomes an empty escape; an unproductive mind does not need rest.
A hobby can be a remedy for mental fatigue resulting from a profession that involves bringing work home. Often, an hour at a hobby will make you able to resume your work. It can be an effective brain-restorer.
The more you have done to take a vacation from, the more purposeful you are, the more rewarding a vacation or a hobby can be. But not just any hobby. It also must meet your need for purpose. Collecting soap from different hotels will not do.
To the extent that a hobby resembles a career, it has the added benefit of a career; you can maintain a purpose over a long period of time. Although people can find pleasure in single occasions, such as a party or a show or even a vacation, this is a pleasure that ends right then and there, with no further consequences. Yet they need relaxation and rest from their constant, single-tracked drive. What they need is another track, but for the same train - that is, a change of subject, but using part of the same method of mental functioning.
A hobby allows the individual hobbyist to remain in his own private world, under his control. Depending on the hobby, he can avoid the dishonesty and irrationality of other people he often must deal with in a career. Nobody can interfere with his hobby, nobody needs to be considered or questioned or worried about. The choices, the work, the responsibility - and the enjoyment - are one's own. So is the great sense of freedom and privacy. For this reason, when one deals with fellow hobbyists, it is on a cheerful, benevolent basis. There is the sense of a "brotherhood" of people with shared values.