Phaedrus - The horse and the boar

The boar, splashing about, muddied the puddle in which the horse used to quench his thirst. A quarrel ensued. The steed, furious with the beast, asked the man for help and taking him on his back, he went back to his enemy. The knight shot arrows at the boar, and, after killing it, it is told that he spoke thus, "I am glad to have brought you help as you had
prayed, for I have caught a prey and found out how useful you are." And
so he forced him to bear the yoke in spite of himself. Then the one, desolated, said, "Fool that I am; I was seeking revenge for a trifle and found slavery."
This fable will advise the wrathful to let themselves be damaged without reacting, rather than give themselves at the mercy of another.

[ Equus sedare solitus quo fuerat sitim,
Dum sese aper volutat turbavit vadum.
Hinc orta lis est. Sonipes iratus fero
Auxilium petiit hominis, quem dorso levans
Rediit ad hostem. Iactis hunc telis eques
Postquam interfecit, sic locutus traditur:
«Laetor tulisse auxilium me precibus tuis;
Nam praedam cepi et didici quam sis utilis».
Atque ita coegit frenos invitum pati.
Tum maestus ille: «Parvae vindictam rei
Dum quaero demens, servitutem repperi».
Haec iracundos admonebit fabula:
Impune potius laedi quam dedi alteri]