Hapiness and Ocupation of Mind
Whether we are in a pleasant or a painful state depends, ultimately, upon the kind of matter that pervades and engrosses our consciousness. In this respect, purely intellectual occupation, for the mind that is capable of it, will, as a rule, do much more in the way of happiness than any form of practical life, with its constant alternations of success and failure, and all the shocks and torments it produces. But it must be confessed that for such occupation a pre-eminent amount of intellectual capacity is necessary. And in this connection it may be noted that, just as a life devoted to outward activity will distract and divert a man from study, and also deprive him of that quiet concentration of mind which is necessary for such work; so, on the other hand, a long course of thought will make him more or less unfit for the noisy pursuits of real life. It is advisable, therefore, to suspend mental work for a while, if circumstances happen which demand any degree of energy in affairs of a practical nature.
Arthur Schopenhauer, in 'Aphorisms for the Wisdom of Life'