How much emphasis do you place on the physiological aspect of attraction?

When you’re pursuing a relationship with someone, do you evaluate your attraction by how your body reacts around him/her? (For example, butterflies in the stomach, weak in the knees, head spinning, heart racing.) Or do you think these kind of reactions are superficial and have little bearing on the actual emotion? How intense do you expect the reactions to be?

I’m dating a guy who I really like, and I am physically attracted to him. I do feel some physiological reactions around him, I always long to touch/kiss him (almost gravitate to him), and I get a feeling like my heart swells. But I don’t feel any serious “magic,” as they say. I’m happy when I see him, but I don’t get butterflies. I like kissing him, but there are no “fireworks.” However, I do feel emotionally attached to him. I just wonder if there should be these intense physiological reactions along with it.