What is the origin of the idiom "black mood" and when to use it?

The origin of the idiom "black mood" can be traced back to the Middle Ages. In medieval times, the word "black" was often associated with negative or dark emotions, including sadness or melancholy. The concept of a "mood" referred to an individual's emotional state or disposition. This expression is typically used when someone is experiencing a prolonged period of profound sadness or despair, often accompanied by a sense of hopelessness or emotional turmoil. It can be used to describe the emotional struggles of individuals dealing with grief, loss, or other challenging life circumstances.