Moral Letters to Lucilius Section 8

Quaeris quod sit amplissimum vitae spatium? Usque ad sapientiam vivere. Qui ad illam pervenit, attigit non longissimum finem, sed maximum. Ille vero glorietur audacter et dis agat gratias interque eos sibi, et rerum naturae inputet, quod fuit. Merito enim inputabit; meliorem illi vitam reddidit quam accepit. Exemplar boni viri posuit, qualis quantusque esset ostendit. Si quid adiecisset, fuisset simile praeterito.

Tu demandes quel est l’âge le plus avancé ? L’âge de la sagesse. Y parvenir c’est avoir atteint non la plus lointaine limite, mais la plus élevée. Que l’homme alors se glorifie hardiment et remercie les dieux en se retrouvant parmi eux, et sache gré autant à lui-même qu’à la nature de ce qu’il a été. Oui, il a droit de s’applaudir d’avoir rendu à la nature une vie meilleure
qu’il ne la reçut. Il a réalisé le modèle de l’homme de bien ; il en a fait voir le caractère et la grandeur : eût-il ajouté à ses jours, il n’eût fait que continuer son passé. Et jusqu’où donc voulons-nous vivre ?

And what, you ask, is the fullest span of life? It is living until you possess wisdom. He who has attained wisdom has reached, not the furthermost, but the most important, goal. Such a one may indeed exult boldly and give thanks to the gods - aye, and to himself also - and he may count himself Nature’s creditor for having lived. He will indeed have the right to do so, for he has paid her back a better life than he has received. He has set up the pattern of a good man, showing the quality and the greatness of a good man. Had another year been added, it would merely have been like the past.