Being attracted to a person is something that most human beings experience. And there are feelings of sadness when the people we love do not respond to our feelings.
Erotomania is a fantasy where one believes that the person he likes keeps the same feelings toward him. Falling in love is good, Delusional is horrible.
This personality disorder is generally or sufferers on average men.
The most visible symptom of a person with erotomania is the stalking behavior of a loved one.
He also tends to insist on maintaining his belief even though his object of love has tried to resist it.