Well, before we get into that, let's briefly delve into the nature of emotions themselves.

Emotions basically consist of two parts: a cognitive component (what you're thinking) and a physiological component (what you're feeling). The cognitive, thinking component determines WHAT emotion you're feeling... while the physiological, feeling component determines the INTENSITY of that emotion.

For example, if you're angry with someone, you're thinking all kinds of "angry" thoughts about that person (He's an idiot! This is not fair! I'm going to kill him!). You're also experiencing certain physiological sensations throughout your body that indicate to you that you're a little more than just displeased (increased heart rate, increased blood pressure, mild sweating, adrenaline surging throughout your veins, etc.). And the more intense the physiological aspects become, the angrier you FEEL.

Okay, so how about love? You meet the girl of your dreams, and you begin thinking: "My God, she's beautiful. She's adorable, charming, and witty. I think I'm in love!" Your body also begins a somewhat automatic reaction to her presence... or maybe even just the thought of her (increased heart rate, increased blood pressure, mild sweating, adrenaline surging throughout your veins, etc.). And the more intensely your body reacts, the more "in love" you feel. And what a wonderful feeling it is.

So... notice anything interesting about the two emotions above? Yes, the physiological components are pretty much the same. The difference between being extremely angry, and being in a state of infatuation or love, has more to do with the cognitive, thinking component, than with the physiological, "feeling" component. You're thinking "angry" thoughts in the first example, and "love" thoughts in the second. Your body is reacting pretty much the same in both instances. And the more intensely your body reacts, the more "angry" or "in love" you feel. (Ever heard that saying that there's a fine line between love and hate?)