Bad days (and the bad emotions they generate) create an effect that is sort of like a game of telephone. Mr. A has a bad day. That night, he comes home and tells his wife, Mrs. A, what a bad day he had. He rants and raves and performs what we typically call "venting." Mrs. A feels so badly listening to him, that the next morning when she goes for a walk with her neighbor Mrs. B, the whole story comes gushing out. She cries on Mrs. B's shoulder, and then goes about the rest of her day not exactly forgetting the whole incident from the night before, but at least feeling a little better. After their walk, Mrs. B has a lunch date with her friend Mrs. C, and Mrs. B's outburst is fresh in her mind, so she tells Mrs. C. At this point, all the anger and sorrow has ebbed from the story; Mrs. B and Mrs. C. feel a bit of pity for Mrs. A and her husband, but they are easily able to shrug and go their separate ways. Later that night, when Mrs. C is sitting at dinner with her husband, trying to think of something to fill the silence at the table, she recalls the story Mrs. B told her and, in a very "You won't believe this" way, gives her own recount. She is so melodramatic in her retelling that Mr. C laughs out loud.
And there you have it: the end of the emotional game of telephone. An event causes an emotion that unleashes a story that transforms that emotion and shifts it from one polar opposite of the emotional spectrum to the other.
These emotional transformations, from sorrow to anger or anger to hilarity, are only possible because the emotions become stories and the stories are told and retold. Ultimately, the transformation is in the telling.