From The Morals of Seneca: A Selection of his Prose, based on the translation by Sir Roger L’Estrange, edited by Walter Clode; London: Walter Scott, Ltd., 1888; pp. 3-5
[3]True happiness is to be free from perturbations; to understand our duties toward God and man; to enjoy the present, without any anxious dependence upon the future; not to amuse ourselves with either hopes or fears, but to rest satisfied with what we have, which is abundantly sufficient; for he that is so wants nothing. The great blessings of mankind are within us, and within our reach; but we shut our eyes, and, like people in the dark, we fall foul of the very thing we search for without finding it. Tranquility is a certain equality of mind which no condition of fortune can either exalt or depress. Nothing can make it less, for it is the state of human perfection: it raises us as high as we can go, and makes every man his own supporter, whereas he that is borne up by anything else may fall. He that judges aright, and perseveres in it, enjoys a perpetual calm; he takes a true prospect of things; he observes an order and measure in all his actions; he has a benevolence in his nature; he squares his life according to reason, and draws to himself love and admiration. Without a certain and unchangeable judgment, all the rest is but fluctuation. Liberty and serenity of mind must necessarily ensue upon the mastering of those things, which either allure or affright us, when, instead of these flashy pleasures (which even at the best are both vain and hurtful together), we shall find 4 ourselves possessed of an excellent joy assured and a continual peace and repose of soul. There must be a sound mind to make a happy man; there must be a constancy in all conditions, a care for the things of this world, but without trouble, and such an indifferency to the bounties of fortune, that either with them or without them we may live content. There must be neither lamentation, nor quarrelling, nor sloth, nor fear, for it makes a discord in a man’s life. He that fears serves. The joy of a wise man stands firm without interruption; in all places, at all times, and in all conditions, his thoughts are cheerful and quiet. Into what dangerous and miserable servitude he falls who suffers pleasures and sorrows (two unfaithful and cruel commanders) to possess him successively! I do not speak this either as a bar to the fair enjoyment of lawful pleasures, or to the gentle flatteries of reasonable expectations. On the contrary, I would have men to be always in good humour, provided that it arises from their own souls, and is cherished in their own breasts. Other delights are trivial; they may smooth the brow, but they do not fill and affect the heart. True joy is a serene and sober motion, and they are miserably out that take laughing for rejoicing. The seat of it is within, and there is no cheerfulness like the resolution of a brave mind, that has fortune under its feet. He that can look death in the face, and bid it welcome; open his door to poverty, and bridle his appetites; this is the man whom Providence has established in the possession of inviolable delights. The pleasures of the vulgar are 5 ungrounded, thin, and superficial; but the others are solid and eternal. As the body itself is rather a necessary thing than a great, so the comforts of it are but temporary and vain; whereas a peaceful conscience, honest thoughts, virtuous actions, and an indifference for casual events, are blessings without end, satiety, or measure.