I often miss a good idea when reading about it for the first
time. But it would leave a mark and over time, I would
reflect and revisit, often more than once, and eventually, I
would get the point.

One such idea was "Flow" as in the title of the book "Flow:
the psychology of optimal experience" by Prof. Mihaly
Csikszentmihalyi. Pavel of StrongFirst gave the book a
stellar review in his Jan 2016 article "The Will To Happiness." That was where I first encountered the concept.
Early 2017, a colleague mentioned a post about "Deep
Work" which cited "Flow." I re-read Pavel's article and
books by the prof and finally got the point in Feb 2018.

From the book, I learnt the word "autotelic" which refers to 
an activity as an end to itself. Aside from this dictionary 
meaning, the word is used to describe one's personality to
be able to enjoy the nuances of activities or to find and
even create variety and, over time, derive an internal sense
of growth. The process of "enjoying the game itself" is the
experience of "Flow." The prof defines a happy life as one
consisting of a lot of flow experiences. If so, I have been
lucky and able to escape to that state in my many pursuits.

Another related concept is "practice." This idea first sunk
in after I listened to Pavel on a Tim Ferriss podcast. When
one practices something, one does it almost for its own
sake. For example, I lift weights not because I want to beat
anyone or break some record. I believe lifting would keep me
from immobility and osteoprosis in old age. That's about it.
Of course, when one's strong, many good things happen, e.g.,
a good image, bragging rights, depression-resistance, etc.,
but I try not to dwell on these. I lift mainly because I still can.

It's probably more revealing to consider what doesn't lead
to flow. My early attempts at improving physical performance
failed miserably and I hated most PE activities. One big
reason was that PE was not regarded as important for
survival and reproduction in the Chinese society. Deep down,
the desire to live is the key for the possibiliy of flow.
The Spartans could show contempt for death but they still had
to tap into the primal instinct to improve their prowess.
The will to happiness depends on that to survive. Flow,
autotelic, and the simple word, practice, are useful and
practical concepts. But again, they make as much sense as
one loves life.

Below I copied from the Wikipedia on the word "autotelic,"
written by the professor. It is a tall order but an ideal
worth aiming at nonetheless. 

    An autotelic person needs few material possessions and
    little entertainment, comfort, power, or fame because so
    much of what he or she does is already rewarding.
    Because such persons experience flow in work, in family
    life, when interacting with people, when eating, even
    when alone with nothing to do, they are less dependent
    on the external rewards that keep others motivated to go
    on with a life composed of routines. They are more 
    autonomous and independent because they cannot be as
    easily manipulated with threats or rewards from the
    outside. At the same time, they are more involved with
    everything around them because they are fully immersed
    in the current of life.[3]