uncertainty -

“The Greeks thought lovesickness was a type of insanity, a view that was adopted by medieval commentators in Europe. In the Middle Ages, the French defined love as a ‘derangement of the mind’ that could be cured by sexual intercourse, either with the loved one or with a different partner,” Coontz writes in her 2005 book, “Marriage, A History: From Obedience to Intimacy, or How Love Conquered Marriage.”