Demi Lovato has admitted she was confused about why it took her a while to become a big success on the radio.
She said: "I had a moment where I was just like, 'What am I doing wrong? I know I can sing. I know I'm talented. How is it that other artists who don't have my vocals ... (are) on the radio? What's taking so long?'
"And I realised, 'Oh, it's hit songs. You need hit songs'."
The 20-year-old has recently released her fourth album, Demi, and it debuted at number three on the Billboard 200 chart.
"We didn't want to put a song on there that was an album filler, so we don't have any songs on there that couldn't be potential singles," she explained.
The star also told how being a judge on the US X Factor has been great for her career.
"It doesn't hurt when you're releasing music and you're in millions of people's homes every week - twice a week," she said. "X Factor has helped me make that transition from being the Disney pop singer ... to the mainstream world."
Demi was on the panel alongside Simon Cowell, LA Reid and Britney Spears last season. However, Britney and LA have now left, and the next series will see Kelly Rowland and Paulina Rubio joining the panel.