Wikipedia says, weltschmerz
denotes the kind of feeling experienced by someone who understands that physical reality can never satisfy the demands of the mind. . . . It is also used to denote the feeling of sadness when thinking about the evils of the world.
The modern meaning of Weltschmerz . . . is the psychological pain caused by sadness that can occur when realizing that someone's own weaknesses are caused by the inappropriateness and cruelty of the world and (physical and social) circumstances.