Looking more closely at some Latin words can be an enlightening experience. I am sure that experience is also the case in other languages.
Take the word "impotens." As you can guess, it has the basic meaning of being impotent: weak, feeble.
But there is another common meaning in Latin that might take you by surprise as it did me:
"not master of himself, unbridled, headstrong, violent, insolent, immoderate, excessive, furious" (source: online Lewis & Short Latin Dictionary).
In other words, you are impotent when you lack self-control. Thus, being impotent is not just a matter of lacking some sort of vital energy but also of not being strong enough to control your vital energy, even if you have plenty of it.
So you lack true power when you cannot control yourself.
Our culture glorifies excess when in fact excess is impotence. This idea of excess as weakness is countercultural in our culture, as it was in much of Roman culture, especially as the empire became richer and unchallenged.
(Image of golden mean in public domain)