From S.T. Coleridge’s Biographia Literaria
It [his exhortation to youthful literati] will be but short; for the beginning, middle, and end converge to one charge: never pursue literature as a trade. With the exception of one extraordinary man, I have never known an individual, least of all an individual of genius, healthy or happy without a profession, i.e. some regular employment, which does not depend on the will of the moment, and which can be carried on so far mechanically that an average quantum only of health, spirits, and intellectual exertion are requisite to its faithful discharge. Three hours of leisure, unannoyed by any alien anxiety, and looked forward to with delight as a change and recreation, will suffice to realize in literature a larger product of what is truly genial, than weeks of compulsion. Money and immediate reputation form only an arbitrary and accidental end of literary labour. The hope of increasing them by any given exertion will often prove a stimulant to industry; but the necessity of acquiring them will in all work of genius convert the stimulant into a narcotic. Motives by excess reverse their very nature, and instead of exciting, stun and stupefy the mind.