Pretty much the human condition. Seneca was writing about it in the first century, Buddhists were talking about it from the inception of their religion.
What do people get for all the toil and anxious striving with which they labor under the sun? All their days their work is grief and pain; even at night their minds do not rest. This too is meaningless. A person can do nothing better than to eat and drink and find satisfaction in their own toil.
From Ecclesiastes, one of the few parts of the Christian scriptures that still interests me.
