It certainly is poetic. I don't know how much of that comes from the translation which will have been done by someone who already "knows" that these letters are important classical texts. If I knew Ancient Greek then maybe I could read it and it would seem like reading people's Facebook messages today.
But if you like that kind of writing, then try writing like that! If you keep at it, your friends will at least to recognise that style of writing as part of you. :-)
There are almost 7.9 billion living people. There are more literate people on the planet than any other time in history. The corpus of private correspondence produced daily is huge, and you will never see more than a tiny sliver of it. There could be a thousand Senecae (in terms of the quality of their private letters) living alongside you, and you would never know it.
Keep in mind, too, that that text is a translation. Seneca didn't write that. A translator named Robin Campbell did. I trust Campbell captured the essence of what Seneca meant, and I'm willing to believe its beauty in English is analogous to the beauty of Seneca's Latin, but who writes like that nowadays? Robin Campbell did in 1969, pretty close to nowadays!
Right about private correspondence however i follow many intellectual blogs on the rationalist diaspora (lesswrong, substack) + reddit and HN and I have never quite seen a blog showing this level. One would have thought internet would make discovering such talents order of magnitudes easier..
I recently read heard some Molière and the verbal virtuoseness is unmatched to anything else I know of.
I didn't knew about Robin Campbell, will give it a try :)
But if you like that kind of writing, then try writing like that! If you keep at it, your friends will at least to recognise that style of writing as part of you. :-)