Every day, in the early afternoon, the Heart and the Brain would sit together on a bench. Their conversations always revolved around each of their woes until finally one afternoon they were both fed up.
As the Heart began to say “I feel-” the Brain cut her off.
"That’s your problem. You feel too much. You see, I think-"
"And that’s your problem," the Heart cut in. "You think too much."
They sat there in silence, each annoyed at the other, for a long while.
Eventually, a little slip of a thing came floating by near their bench. It was wearing a faded gray cloak and looked like the wind would blow it away at any moment, but it kept true to the path in front of it.
"Excuse me," said the Brain. The thing stopped in front of them, hovering patiently. "What kind of organ are you?"
"I’m not an organ at all," came an airy voice from within the folds of the cloak. "I’m an Emotion."
This was a new concept to both the Heart and the Brain. They thought it over for a few moments before the Heart spoke up.
"What’s an Emotion?" she asked.
"We are the feelings created when you and the Brain work together," the Emotion explained.
"I’m sorry, I don’t understand," the Brain admitted. The Emotion nodded patiently.
"Let me give you some examples. When you feel very strongly about something, but the Heart doesn’t, and you try to force her to, the Emotion you both create is Disappointment. Conversely, when the Heart feels much more than she should, and you are prudent and try not to let her, the Emotion you create is Sorrow," the Emotion told them.
They nodded, understanding both situations well. “And every once in a while, the best kind of accident happens, and you both feel strongly about something. When that something turns out to be the right thing, the Emotion you create is called Love.”
The Heart and the Brain sighed wistfully, finally having a name for that fleeting feeling they’d both felt on occasion.
"But which kind of Emotion are you?" asked the Brain.
The Emotion sighed sadly. “My name is Regret.”
"And what do we feel to create you?" the Heart was curious.
"Ah, that’s just it," Regret whispered. "I am born when neither of you dare to feel a thing."