The 'Skyscraper' singer joined the show's judging panel for the current season, replacing season one's Nicole Scherzinger and Paula Abdul.
In an interview with Parade, Lovato stressed that she has dedicated herself to helping acts like CeCe Frey and Paige Thomas succeed on the series.
Describing it as "fun and exciting, but really stressful", she said: "I was surprised at how emotionally invested I became. It hurts to see them go, especially when I know their potential."
Lovato also said that she felt intimidated by being the youngest judge on The X Factor USA's second season at just 20 years old.
"It's an honour to sit next to [the judges] because they're legends, but I'm a southern girl with a big mouth, and I speak my mind," the star teased.
Simon Cowell was coy when recently questioned about Lovato's future on the reality competition, but did describe her as a "fun" colleague.
LA Reid has announced that he will not return for The X Factor USA's third season. He will instead focus on running Epic Records.
The X Factor USA's two-night grand finale will air on Wednesday and Thursday at 8/7c on Fox.
Photo gallery - X Factor USA semi-final: