Grace VanderWaal knows how to take advantage of a golden opportunity. At just 12 years old, the singer graced the stage of America's Got Talent where she performed an original song with her ukulele. Within minutes, Simon Cowell called her the next Taylor Swift while fellow judge Howie Mandel pressed the Golden Buzzer, advancing her to the live shows. Now, more than six years after winning NBC's summer competition show, Grace is living her acting and singing dreams. But that's not to say it's always been an easy road.  "Looking back, I have definitely faced the mental repercussions of that growing up," the 18-year-old exclusively shared with E! News. "I feel...