“The indefatigable pursuit of an unattainable perfection, even though it consist in nothing more than the pounding of an old piano, is what alone gives a meaning to our life on this unavailing star.”

Source: Summa Theologica (1265–1274), I–II, q. 3, art. 8 co

The Secret of the Machines, Stanza 8.
Other works

The Story of Australia's People: The Rise and Fall of Ancient Australia (2015)

https://www.youtube.com/watch?v=QoTrlcR4KyA Youtube

If This Is a Man (1947)
Context: Sooner or later in life everyone discovers that perfect happiness is unrealizable, but there are few who pause to consider the antithesis: that perfect unhappiness is equally unattainable. The obstacles preventing the realization of both these extreme states are of the same nature: they derive from our human condition, which is opposed to everything infinite. Our ever-insufficient knowledge of the future opposes it: and this is called, in the one instance, hope, and and in the other, uncertainty of the following day. The certainty of death opposes it: for it places a limit on every joy, but also on every grief. The inevitable material cares oppose it: for as they poison every lasting happiness, they equally assiduously distract us from our misfortunes and make our consciousness of them intermittent and hence supportable.

Source: The Doctrine of the Mean

Closing sentence of the Preface to the general science (1677) (in P. Wiener (ed.), Leibniz Selections, Macmilland Press Ltd, 1951).

Heimsljós (World Light) (1940), Book Two: The Palace of the Summerland

Source: Foreword, Initiation, The Perfecting of Man (1923)