Free yourself from common foolishness. This requires a special sort of sanity. Common foolishness is authorized by custom, and some people who resisted the ignorance of individuals were unable to resist that of the multitude.

[Librarse de las necedades comunes. Es cordura bien especial. Están muy validas por lo introducido, y algunos, que no se rindieron a la ignorancia particular, no supieron escaparse de la común.]

Baltasar Gracián y Morales (1601-1658) Spanish Jesuit priest, writer, philosopher

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 209 (1647) [tr. Maurer (1992)]
    (Source)

(Source (Spanish)). Alternate translations:

Not to imitate the folly of others is an effect of rare wisedome; for whatever is introduced by example and custome, is of great force. Some who have guarded against particular ignorance, have not been able to avoid the general.
[Flesher ed. (1685)]

Keep yourself free from common Follies. This is a special stroke of policy. They are of special power because they are general, so that many who would not be led away by any individual folly cannot escape the universal failing.
[tr. Jacobs (1892)]

To keep free from the popular inanities, marks especially good sense. They are highly esteemed because so well introduced, and many a man who could not be trapped by some particular stupidity could not except the general.
[tr. Fischer (1937)]