Whats the difference between love and hormones?

I believe in true love, in the ability to care so much for a another person that you're willing to sacrifice your own happiness for theirs. But what about being in love? You know like the whole romantic, sensual kind; I'm not sure it exists. Could that type of attraction only be a chemical reaction stimulated by the brain in order to ensure the survival of our species? I want to believe in it, but it seems that being in love isn't really love at all. It's temporary. So many people who think they're really in love end up breaking up, getting divorced, or basically not feeling that way for very long. I'm not saying true love doesn't exist, but I think people are getting their hormones mixed up with love. Obviously real love and "being in love" are two different things, as one seems to be only temporary. I don't know if I'm right, though. In fact, I have no idea. So prove me wrong please...whats the difference between hormones and "being in love"?