Neither all bad nor all good. A certain sage reduced the whole of wisdom to the golden mean. Carry right too far and it becomes wrong. The orange squeezed completely dry gives only bitterness. Even in enjoyment you shouldn’t go to extremes. The intellect itself will go dry if pressed too hard, and if you milk a cow like a tyrant you will draw only blood.

[Nunca apurar, ni el mal, ni el bien. A la moderación en todo redujo la sabiduría toda un sabio. El sumo derecho se hace tuerto, y la naranja que mucho se estruja llega a dar lo amargo. Aun en la fruición nunca se ha de llegar a los extremos. El mismo ingenio se agota si se apura, y sacará sangre por leche el que esquilmare a lo tirano.]

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

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 82 (1647) [tr. Maurer (1992)]
    (Source)

(Source (Spanish)). Alternate translations:

Not to pry too much neither into good nor evil. A wise man comprehended all his wisedom in this Precept, ne quid nimis, nothing too much. Too strict a justice degenerates into injustice. The Orange that is too much squeezed, yields a bitter juice. Nay in enjoyment, we ought never to go to either of the two extremes. Wit itself is exhausted by too much straining. By endeavouring to draw down too much milk, bloud is often fetched.
[Flesher ed. (1685)]

Drain Nothing to the Dregs, neither Good nor Ill. A sage once reduced all virtue to the golden mean. Push right to the extreme and it becomes wrong: press all the juice from an orange and it becomes bitter. Even in enjoyment never go to extremes. Thought too subtle is dull. If you milk a cow too much you draw blood, not milk.
[tr. Jacobs (1892)]

Drink nothing to the dregs, either of the bad, or of the good, for to moderation in everything has one sage reduced all wisdom. Too great justice become injustice, and the orange, squeezed too hard, turns bitter; even in enjoyment, do not go too far. The spirit itself grows weary if worked too long, and he draws blood instead of milk, who milks too hard.
[tr. Fischer (1937)]