“It is unwise to be too sure of one's own wisdom. It is healthy to be reminded that the strongest might weaken and the wisest might err.”

"In Praise of the Fighters" (song)
Variant translation: There are men who struggle for a day and they are good.
There are men who struggle for a year and they are better.
There are men who struggle many years, and they are better still.
But there are those who struggle all their lives:
These are the indispensable ones.
As quoted in Democracy Unbound : Progressive Challenges to the Two Party System (1997) by David Reynolds; also quoted by Cuban musician and poet Silvio Rodríguez before his song "Sueño con serpientes".
Also quoted by Eduardo Galeano (Uruguayan writer) to describe Nestor Kirchner as he received the notice of his death.
The Mother (1930)

Letter to Fanny Burney; Charlotte Barrett (ed.) Diary and Letters of Madame d'Arblay (1854) vol. 2, p. 3.

Source: Vorkosigan Saga, Barrayar (1991)

Wisdom Is —
Grooks

Bacchæ l. 1150.

Referring to her teenage diary, in an interview in Movie magazine (July 1983)

Revelations of Divine Love (c. 1393), Chapter 1
Context: Our Lord God willeth we have great regard to all the deeds that He hath done: in the great nobleness of the making of all things; and the excellency of man’s making, which is above all his works; and the precious Amends that He hath made for man’s sin, turning all our blame into endless worship. In which Shewing also our Lord saith: Behold and see! For by the same Might, Wisdom, and Goodness that I have done all this, by the same Might, Wisdom, and Goodness I shall make well all that is not well; and thou shalt see it. And in this He willeth that we keep us in the Faith and truth of Holy Church, not desiring to see into His secret things now, save as it belongeth to us in this life.

Bacchæ l. 882
Variant translation: Slowly but surely withal moveth the might of the gods.

Source: Hunter/Victim (1988), Chapter 18 (p. 100)