I should have replied to your other thread Don, but I'll put it here!
Regarding mens sana in corpore sano, there is a history there that DeWitt doesn't tease out for us. Your instincts are correct; Juvenal's famous line is Stoical;
QuoteDisplay MoreYou should pray for a healthy mind in a healthy body.
Ask for a stout heart that has no fear of death,
and deems length of days the least of Nature's gifts
that can endure any kind of toil,
that knows neither wrath nor desire and thinks
the woes and hard labors of Hercules better than
the loves and banquets and downy cushions of Sardanapalus.
What I commend to you, you can give to yourself;
For assuredly, the only road to a life of peace is virtue.
The Epicurean response was offered by Horace, which I'll paraphrase as I cannot find the source just now;
Let me ask Jupiter only for what is in his power to give—it would be absurd to ask for a contented mind, as I can provide that for myself.
You don't need to ask for a stout heart that has no fear of death; Epicurus suggested that that is what philosophy is for!