Why Are Breakups So Painful?

In today’s world, it is very common to see relationships end in a breakup or divorce. In the past, divorce was almost unheard of, but today in the United States, over half of all marriages end in divorce, and most people have experienced a few breakups. Whether it was a pleasant or unpleasant relationship, a breakup always seems to hurt very deeply, almost as if one is losing a part of themselves. Why is this? Should it not be that the end of an unpleasant relationship feels pleasant or freeing...