In the army. Seneca, Epistles 4.37.1-2

Seneca tells Lucilius how to be a philosopher in the army.

Quod maximum vinculum est ad bonam mentem, promisisti virum bonum, sacramento rogatus es. Deridebit te, si quis tibi dixerit mollem esse militiam et facilem. Nolo te decipi. Eadem honestissimi huius et illius turpissimi auctoramenti verba sunt: uri, vinciri ferroque necari. Ab illis qui manus harenae locant et edunt ac bibunt quae per sanguinem reddant cavetur ut ista vel inviti patiantur: a te ut volens libensque patiaris. Illis licet arma summittere, misericordiam populi temptare: tu neque summittes nec vitam rogabis; recta tibi invictoque moriendum est. Quid porro prodest paucos dies aut annos lucrificare? sine missione nascimur.

You promised the army a good man, and now the time is come to honor that solemn oath, the strongest tie that binds us to a sound mind. If anyone ever tells you that military service is soft and easy, he is definitely mocking you. I don't want you to be deceived. Your real wages are best summed in these words, brutally honest and awful: being burned, bound, and put to the sword. Those who enter the arena as gladiators, eating and drinking what they earn with blood, must take care to avoid suffering such trials unwillingly. See that you undergo them freely, by your own choice. The gladiators are allowed to surrender arms, tempting the mercy of the people. You will not surrender, nor beg anyone for your life. You must die unconquered, like a proper soldier. What is the point of gaining a few more days or years? We are not born to reach retirement.