A character in the novel I read at bedtime, At Home in Mitford, used the saying 'The firefly only shines when on the wing' implying that when it stops flying it stops shining and that humans can take the lesson from this that they must stay busy or at least engaged in life or 'go dark'.
This haunted me all day and I even did a riff on the theme with my free write today to the effect that to keep the words flowing and the ideas glowing I must keep my fingers moving.
Then the concept of doing my Sunday Serenity on the theme occurred and as I searched for images I found many of the little beetles (not flies after all with their bellies all lit as they rested on a leaf. So much for the truth in that truism or the apt in that aphorism.
I can't shake it. It feels true.