I have come to this thought:
All of life is an either incognizant or cognizant state of searching to
find and or maintain sufficiency. - David Dorrell, 2010
Sufficiency is not contentment (although it may be), it is not happiness (although it may be), it may be the search for the strength to get through the day, the night, or a death (even your own). Life is the search for sufficiency. We may never find it.
Plants grow roots to find water; babies instinctively breathe; humans work for a living all of this is sufficiency.
We may think we seek happiness, but what we are actually seeking is new levels of sufficiency. To hold happiness changes its nature; the state of being happy is transient because each time it is attained, it places a new goal for meeting happiness.
Arts, science, mathematics all just raise us to a different level of sufficiency. We surround ourselves with aesthetics that please us, our appreciation of these things, that song, that painting, that book, that movie, grow familiar, stale. We gain new knowledge of our world, but there is always more to learn.
Even in heaven, happiness must be a transient state for even the slightest drop in happiness would then have to be considered sadness, but the search for sufficiency could still be constant.