Thanks for sharing. The comparison of a wise man to a physician seems to be a common technique back then (Cicero also uses it). Seneca's essays are indeed outstanding. The above quotes sound like they are from "On th constancy of the wise man". As that's one of the 2 essays Seneca wrote to Serenus.

I love the other essay that he wrote to Serenus, "On the tranquility of the mind". I shared a quote (and a translation) here[1] in the past.

[1] https://news.ycombinator.com/item?id=25415296