It's like a narcotic.

"I´ve been in love before, it´s like a narcotic. At first it brings the euphoria of complete surrender. The next day you want more. You´re not addicted yet, but you like the sensation, and you think you can still control things. You think about the person you love for two minute then forget them for three hours. But then you get usedd to that person, and you begin to be completely dependent on them. Now you think about him for three hours and forget him for two minutes. If he´s not there, you feel like an addict who can´t get a fix. And just as addicts steal and humiliate themselves to get what they need, you're willing to do anything for love."
   
                                                                                                        Paulo Coelho.