It is evolution's way of making sure that sexual partners meet and mate, then give their child the care it needs to be healthy and make loving attachments of its own. This isn't a simple or fast process. The human brain is so complex, the mind so ingenious, that biology and experience work hand in hand.
People usually undergo a series of crushes, infatuations, and loves between infancy and adulthood.
They learn to make magnetic attachments, whose power they feel in their cells, in their bones. Thinking about the loved one steers their every thought, and they would die rather than break the force field of their devotion. It is as if they were two stars, tightly orbiting each other, each feeding on the other's gravity. Because nothing and no one in time or creation seems to matter more, a broken relationship rips the lining from the heart, crushes the rib cage, shatters the lens of hope, and produces a drama both tragic and predictable. Wailing out loud or silently, clawing at the world and at one's self, the abandoned lover mourns.