One day is equal to every day [Unus dies par omni est.]--Heraclitus, the obscure.
Almost nothing so boring as old people speaking to young people about old age and general decay. Yet, this is the 'hook' of Seneca's twelfth Letter, in which he goes out of his way to present himself as an angry old man who sees decay and death everywhere--nothing like the image of Stoic, apathetic wisdom one might expect. More important, he shows the persona 'Seneca' failing at enjoying the available life's variety of pleasures (marked by different Latin words, e.g, delectavit, voluptatis, iucundissima, etc). It might be the case that the old cannot really avoid looking death in the face, but it is not obvious that we all must fundamentally do so, especially because Seneca himself seems to make a hash of it. While the letter is nominally addressed to the young Lucilus, it is really an admonition to himself to embrace and love [complectamur...et amemus] old age. In recounting his foibles (and other aged men), he wishes to become a true friend of himself such that he is capable of moderated love (sans madness) (recall Letter 9).
It is, after all, not shameful [inprobe] to hope for another day, every day, in old and young alike. (In recounting his foibles, Seneca does not name his more shameful desires.) One might think such lack of shame, which is constituted by the recognition of a binding norm one fails to live up to,* is an instance of living without necessity. But that can't be quite right because in context Seneca treats the denial of necessity as equal to the possibility of ending one's life rather than the hope for another day.
Now, hope is how we mark an uncertain good (recall the tenth letter). So, while not shameful, the wish for another day cannot give us durable and, thus, the right sort of pleasure. As Seneca puts it, he is "happiest, and is secure in his own possession of himself, who can await the morrow without anxiety." In this letter, Seneca leaves unclear how that excellent state, in which each awakening day is pure profit [lucrum], is achieved. Given that for Seneca it is constitutive of the ordinary market place that its goods are uncertain, it is quite clear that Seneca has slipped her into his alternative axiology (recall letter 1 and these others), one marked, as it happens, by well-formed feelings [conscientia bona].
Above I have already suggested that re-telling the story of his decay plays a role in re-shaping Seneca's self-orientation. I infer this from the fact that Seneca's narrative includes his own, confessional commentary on his mis-deeds. How exactly this is supposed to work is left unclear, although the psychological mechanism is probably familiar to most of us.
Much of the letter is given over to an extended commentary on the saying of Heraclitus quoted at the head of this post. In fact, Seneca offers three different interpretations, including a metaphysical-geometric one in his own voice, and at least two other ones attributed to unnamed others (including one flat-footed, and one more poetic). It appears that all three interpretations agree with or at least mutually support each other in implying that "every day ought to be regulated as if [tamquam] it closed the series, as if it rounded out and completed our" lives such that one can invoke Virgil's "I have lived; the course which Fortune set for me is finished."
It is, in fact, striking how many voices are allowed into this letter; in addition to the two unnamed others and the persona 'Seneca,' there are Lucilus (whose hypothetical objections are introduced) and brief exchanges with his bailiff and house-slave. That is, Seneca is not afraid of polyphonia.
Seneca needs and embraces poetry for that 'as if,' but -- like a young charmer -- he only hints at its songs.
* In the preceding letter we were shown such good shame in the spirited young (recall).