Miley Cyrus has a condition called tachycardia, which causes her heart rate to speed up, she reveals in her new autobiography, Miles to Go.
"The type of tachycardia I have isn't dangerous. It won't hurt me, but it does bother me," she writes. "There is never a time onstage when I'm not thinking about my heart."
Cyrus also dedicates a chapter to her "Prince Charming," who appears to be ex Nick Jonas.
"Wow! I was so in love," she says. "Do you know what I'm talking about? The kind of love where the sun could shine or not shine all day long and you wouldn't care."
After they split, she penned "7 Things I Hate About You."
"I was angry when I wrote 7 Things," she says. "I wanted to punish him, to get back at him for hurting me. It starts with a list of what I 'hate.' But I'm not a hater. My heart knew from the start that it was going to turn into a love song. Why does he get a love song? Because I don't hate him."
The 16-year-old bites back at the criticism she's received after controversial moves like posing topless in Vanity Fair and appearing in controversial photos that offended Asian people.
"I try to be a good role model," she writes. "and that's why I think it's too bad that lots of people hope to make money off my mistakes."