Is life worth living ? Why ? Assume science makes you immortal, what will you then do for eternity ? Such questions help us to put into perspective just what is satisfying about life and what we would rather discard. But it also highlights that we would not wish to just repeat the same things over and over again - production line style.
Nature is passive, humans are not. That message means that the value of our lives is a fluid quantity. It depends upon many dynamic aspects, relating not only to our own attitudes but to those of our society and our physical or environmental context. As a species we have far more say in our own Quality of Life than other creatures, indeed since we base much of our perceived social fitness on abstract ideas of worth we are in a position to change this fitness globally, almost overnight.