No business without pain. Seneca, Epistles 5.42.5-7

Seneca advises Lucilius to avoid thinking of any business as being profitable, or convenient. Mortal creatures always conduct business at a loss, in terms of time, and so we should not regard any business we engage as being entirely free, or pleasant. Our engagement will impose limits, which are natural to our existence as mortal creatures, and we want to notice these: pain shows us where they are.

Meministi, cum quendam affirmares esse in tua potestate, dixisse me volaticum esse ac levem et te non pedem eius tenere sed pinnam? Mentitus sum: pluma tenebatur, quam remisit et fugit. Scis quos postea tibi exhibuerit ludos, quam multa in caput suum casura temptaverit. Non videbat se per aliorum pericula in suum ruere. Non cogitabat quam onerosa essent quae petebat, etiam si supervacua non essent. Hoc itaque in his quae affectamus, ad quae labore magno contendimus, inspicere debemus, aut nihil in illis commodi esse aut plus incommodi: quaedam supervacua sunt, quaedam tanti non sunt. Sed hoc non pervidemus et gratuita nobis videntur quae carissime constant. Ex eo licet stupor noster appareat, quod ea sola putamus emi pro quibus pecuniam solvimus, ea gratuita vocamus pro quibus nos ipsos impendimus. Quae emere nollemus si domus nobis nostra pro illis esset danda, si amoenum aliquod fructuosumve praedium, ad ea paratissimi sumus pervenire cum sollicitudine, cum periculo, cum iactura pudoris et libertatis et temporis; adeo nihil est cuique se vilius.

Do you recall what happened before, when you told me that a certain man was in your power? How I said that he was fleet, a flyer sure to break free, and that you had him not by the foot, but merely the tip of the wing? I lied: you had him by the scruff—a handful of feathers, at least, which he shed as he fled your grip. You know what games he gave you then, how oft he tempted the ruin poised over his head. Hurtling through others' woes, he didn't see how he rushed to his own doom. He never reflected on how burdensome his requests for aid were, even though he had good reason to make them. So in every serious endeavor, every project we pursue with great labor, we must keep this one objective in mind: our efforts must either be utterly inconvenient, or give us more inconvenience than not. Some things are unnecessary; others, not so much. We inevitably overlook this fact, and things that cost us most dear appear free and easy. Hence our notorious stupidity, evident in the fact that we only consider ourselves to have purchased things for which we have paid money, calling stuff free when we buy it at the expense of our own lives and selves. Things that we would never be willing to acquire, if we had to give up a home or some pleasant and fruitful estate for them, we are absolutely prepared to procure at the loss of our manners, our freedom, and our time, with worry and danger added to the bill as interest. Nothing is more worthless to any one of us than his own self.