Unrequited love makes sense to the person who longs for someone who does not love them in return. It can happen to anyone. Hollywood stars are often the targets of unrequited love. However, when it becomes obsessive, the danger is that people can start to feel that that they can only become complete and fulfilled through being with the object of their longing. Or some people feel without that union, their life loses all meaning. Once that happens, the likelihood of depression becomes greater and that's not healthy in anyone's book.

Unrequited love is love that is not openly reciprocated or understood as such, even though reciprocation is usually deeply desired

The question seems to be too profound to be answered in short...