In order to not find life unbearable, you must accept two things: the ravages of time, and the injustices of man.
 
[Il y a deux choses auxquelles il faut se faire, sous peine de trouver la vie insupportable. Ce sont les injures du tems et les injustices des hommes.]

Nicolas Chamfort (1741-1794) French writer, epigrammist (b. Nicolas-Sébastien Roch)

Products of Perfected Civilization [Produits de la Civilisation Perfectionée], Part 1 “Maxims and Thoughts [Maximes et Pensées],” ch. 2, ¶ 115 (1795) [tr. Parmée (2003), ¶ 95]
    (Source)

(Source (French)). Alternate translations:

There are two things to which we must become inured on pain of finding life intolerable: the outrages of time and man's injustice.
[tr. Mathers (1926)]

There are two things that one must get used to or one will find life unendurable: the damages of time and the injustices of men.
[tr. Merwin (1969)]

There are two things that a man must reconcile himself to, or he will find life unbearable: they are the injuries of time and the injuries of men.
[tr. Siniscalchi (1994)]