Sure to be a love story

Boy: Okay, so I really like this girl, but I'm not sure what I should do...
girl: You should follow your heart.
boy: What does my heart say?
girl: I don't know, I'm not your heart...
boy: True, but you're most of it.
boy:im gonna give you a kiss you'll never forget.
girl:& what if i do forget?
boy:then i'll kiss you again.
girl: here, i got another riddle.
boy:go for it.
girl: what makes you heart beat faster, gets you sweating, & keeps you alive?
boy: ........................
girl: EXERCISE! get it?
boy: ......................
girl: whats the matter?
boy: i was certain the answer was you.