JK Galbraith, rather surprisingly, pointed out (in his Ambassadors Journal) that you cannot stay successful as a woman in the world of work:
If energy goes, & what little is left is expended on the basics of feeding & keeping oneself clean, that's it, you've had it
This happens to everyone, with age - Raymond Biggs recently said in an interview that one of the problems with age was the amount of time you take ‘just living’
You can lose this mysterious energy at any age, usually though not always in the wake of an obvious & diagnosed illness. Galbraith noted that this was a particular tragedy for women because, on the whole & even in this day & age, it is more likely that a man will be able to rely on others to help him cope with the basics. They do not even necessarily have to be married or have a family. Women are usually quite happy to work for a man, wash his socks. For a woman it can be difficult. There are even still taboos about washing another womans personal clothing
As an interesting byway to these musings I looked up the word stamina
To my surprise I found that it comes from stamen, ‘The thread spun by the Fates at a person's birth’ & then was used to mean a warp thread in weaving - Pliny applied it to the stamens of the lily
Other things being equal the duration of life, unless cut short by violence or disease, was supposed to depend on this. Its use in the sense of ‘vigour of bodily constitution, staying power’ is more recent
Thanks to the OED for information on stamina
