What is the origin of the idiom "cry one's heart out" and when to use it?

The phrase "cry one's heart out" can be traced back to at least the 19th century. Its origin lies in the figurative use of the word "heart" to represent the seat of emotions and deep feelings. This expression can be used in personal narratives, literature, movies, or conversations to depict moments of profound emotional vulnerability and catharsis. It can describe someone crying alone in their room, seeking comfort from a trusted friend while pouring out their heart, or experiencing a moment of deep emotional connection.