There may, in fact, be a deeper connection between happy crying and sad crying: They are both a response to emotional extremes, which suggests that tears help bring us back to equilibrium. Overwhelming negative emotion is important—even lifesaving—in a crisis like being separated from loved ones or being under threat; it creates the impulse to act with force or immediacy. But staying in this state isn’t helpful beyond the immediate crisis (nor is it pleasant), so we seek to reduce stress and improve our mood—which crying can do quite effectively. Some researchers argue that we also need to reset emotionally when things are just too wonderful. Overwhelming joy feels great, but it distracts us from the business of life. And ongoing rapture would be exhausting.
Cry Me a River. It's Good For You. - The Atlantic
