There are two things that can make ones heart and stomach play musical chairs. One of those things is a roller coaster, the other is romance.
To give you a visual, here is a picture of the scariest roller coaster I could find on the net (graysagedotcom):

For some people, like myself, a roller coaster is scary shit.
The roller coaster makes your heart soar, drop, beat faster, and * gasp * stop for a second or two. At each turn your heart beats stronger, at each twist it leaps further out until you think you will see it fly out of your chest, right there before your eyes, and powerless to do anything about it as the coaster brings you around and the sky becomes down and down becomes up.
So it is in matters of the heart (romantic matters that is) you feel it beat with excitement as you think it’s safe to lunge ahead, and do. And, as you feel the first fear of non-reciprocated feelings, rejection, or worse….your stomach and heart quickly change places as they do when the coaster turns and twits and throws you upside down. You think you will certainly lose control of your vital bodily functions. You don’t know how to hang on; you feel you’re flying off the rails and fight to trust the mechanics of it all as the pavement threatens, below you, a rude and painful experience.
For some people romance is also scary shit. You’re afraid of falling, afraid of heights, and the adrenaline rush makes you light in the head and the cold sweat of impending doom washes over you at any sign of anything resembling failure; just as the roller coaster ride jumbles your insides. However, if you can survive the ride, the warm gush of that adrenaline flowing back to where it belongs leaves you with a fuzzy sense of accomplishment and joy.
Or, perhaps it’s the effects of stomach and heart playing musical chairs and it really all is an illusion.

Salon.com
Comments
Enjoyed your comparison of the two themes.
R