A helluva high note

Kara DioGuardi is an award-winning hitmaker, a savvy record executive, and a successful music publisher whose songs have been recorded by such superstars as Pink, Britney Spears, Christina Aguilera, Gwen Stefani, Santana, Steven Tyler, and many others. She was also the feisty fourth judge on American Idol. But success wouldn't have happened for this songwriter, artist, and producer without the dark times of defeat. Kara not only writes about what it was like to collaborate with some of our favorite performing artists, she also opens up about everything from her struggles with debilitating…