The Source of Gloominess
Humility
Rav Pinchos taught that one of the roots of gloominess is pride. An arrogant person thinks the world owes him honor and respect. He always feels slighted, believing that people look down on him and snub him, and so he is always in a somber mood. A humble person cheerfully accepts everything that comes his way.
Source: Medrash Pinchos