About this passageFrom a dialogue that opens with Seneca's friend Serenus describing his own unsettled state in unusual detail, and asking what to do about it. This is part of the answer. The Latin title is De Tranquillitate Animi, and the tranquillity it describes is treated throughout as something maintained rather than achieved — the dialogue ends by saying none of the advice holds without continual attention.
It also proves a fertile source of troubles if you take pains to conceal your feelings and never show yourself to anyone undisguised, but, as many men do, live an artificial life, in order to impose upon others: for the constant watching of himself becomes a torment to a man, and he dreads being caught doing something at variance with his usual habits.
And, indeed, we never can be at our ease if we imagine that everyone who looks at us is weighing our real value: for many things occur which strip people of their disguise, however reluctantly they may part with it, and even if all this trouble about oneself is successful, still life is neither happy nor safe when one always has to wear a mask.
But what pleasure there is in that honest straightforwardness which is its own ornament, and which conceals no part of its character?
In plainer words
Hiding how you feel is its own source of trouble. If you never let anyone see you undisguised, and live a performance to manage what people think, then watching yourself becomes the torment. You start dreading being caught out of character. You can never relax, because you assume everyone looking at you is appraising you. And things happen that pull the disguise off anyway. Even if you get away with it completely, a life spent wearing a mask is neither happy nor safe. Compare that with plain honesty, which needs no decoration and has nothing to keep back.
A restatement in modern English, written for this collection. The passage above is the text; this is one way of putting it.