sophrosyne

"Sophrosyne (σωφροσύνη) is a Greek philosophical term etymologically meaning moral sanity and from there self control or moderation guided by true self-knowledge.

Greeks upheld the ideal of sophrosyne, which means prudence and moderation but ultimately its complex meaning, so important to the ancients, is very difficult to convey in English. It is perhaps best expressed by the two most famous sayings of the oracle at Delphi: "Nothing in excess" and "Know thyself.""

I'm still finding that I don't know myself as well as I thought I did.