zestlessness

zestless +‎ -ness

zestlessness (uncountable)

1. The state or condition of being zestless; lack of passion or enthusiasm.
   • 1932, Pearl S. Buck, Sons, Wakefield, RI: Moyer Bell, 1997, Chapter 15, p. 149,

     But now, pondering all this during these weeks of his despondency he grew frightened at his own zestlessness, and he did not even care to eat so much as he had, and when he found his appetite for food waning he was frightened lest he die too soon, and he said to himself that he must rid himself of some of his troubles.