Letters 74.10

Whoever makes up his mind to be happy should conclude that the good consists only in that which is honourable. For if he regards anything else as good, he is, in the first place, passing an unfavourable judgment upon Providence because of the fact that upright men often suffer misfortunes, and that the time which is allotted to us is but short and scanty, if you compare it with the eternity which is allotted to the universe.

Seneca, Letters to Lucilius 74.10, translated by Richard Mott Gummere