Enchiridion 13

If you wish to make progress, then be content to appear senseless and foolish in externals, do not make it your wish to give the appearance of knowing anything; and if some people think you to be an important personage, distrust yourself. For be assured that it is no easy matter to keep your moral purpose in a state of conformity with nature, and, at the same time, to keep externals; but the man who devotes his attention to one of these two things must inevitably neglect the other.

Epictetus, Enchiridion 13, translated by W. A. Oldfather

If you would improve, submit to be considered without sense and foolish with respect to externals. Wish to be considered to know nothing: and if you shall seem to some to be a person of importance, distrust yourself. For you should know that it is not easy both to keep your will in a condition conformable to nature and (to secure) external things: but if a man is careful about the one, it is an absolute necessity that he will neglect the other.

Epictetus, Enchiridion 13, translated by George Long

If you wish to make progress, you must be content in external matters to seem a fool and a simpleton; do not wish men to think you know anything, and if any should think you to be somebody, distrust yourself. For know that it is not easy to keep your will in accord with nature and at the same time keep outward things; if you attend to one you must needs neglect the other.

Epictetus, Enchiridion 13, translated by P. E. Matheson