Even when you are right, it is good to make concessions: people will recognize you were right but admire your courtesy. More is lost through holding on than can be won by defeating others. One defends not truth but rudeness.

[Aun en caso de evidencia, es ingenuidad el ceder, que no se ignora la razón que tuvo y se conoce la galantería que tiene. Más se pierde con el arrimamiento que se puede ganar con el vencimiento; no es defender la verdad, sino la grosería.]

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

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 183 (1647) [tr. Maurer (1992)]
    (Source)

(Source (Spanish)). Alternate translations:

It is civil to yield, even in those things wherein we have greatest reason and certainty: for then all know, who had reason on their side: and besides the reason, Gallantry is also discovered in the procedure. There is more esteem lost, by a wilfull resistence, then there is got by carrying it by open force. For that is not so much a defending of truth, as a demonstration of Clownishness.
[Flesher ed. (1685)]

Even in cases of obvious certainty it is fine to yield: our reasons for holding the view cannot escape notice, our courtesy in yielding must be the more recognised. Our obstinacy loses more than our victory yields: that is not to champion truth but rather rudeness.
[tr. Jacobs (1892)]

Even with the proof on your side, it is well to make concession, for your reasons are known and your gentlemanliness is recognized; more is lost in contention than can be gained in consummation, for such does not defend the truth, but only exhibits bad manners.
[tr. Fischer (1937)]