Does real love really exist?

I've been wondering... If I really love a person, I would only want the best for them, right? So, if they tell me that they found someone new who is better for them than I am, I should be absolutely happy for them as I would only want the best. Truth is, I would be absolutely heartbroken and NOT happy for them. Did I really love that person then? Or did I love a potential and only became attached?