Flow is often overused, but I think it's worth defining because it might help people find that thing worth doing.
The psychologist Mihaly Csikszentmihalyi describes the experience as being completely involved in an “activity for its own sake.”
“The ego falls away. Time falls away. Every action, movement, and thought follows inevitably from the previous one. Your whole being is involved, and you’re using your skill to the utmost.”
Even with this definition it's hard to find your thing. ITS HARD WORK! And even if you find your thing, it's not like we feel like doing it every single freakin day.
I came across this quote the other day. I think it hits really well into your article. And our modern idea of flow.
“I don't like work--no man does--but I like what is in the work--the chance to find yourself. Your own reality--for yourself not for others--what no other man can ever know. They can only see the mere show, and never can tell what it really means.”