'Roar' beauty Katy Perry has opened up about the song she wrote in response to her divorce from British funnyman, Russell Brand. 

The pair's split impacted the superstar and she penned a track named 'By The Grace Of God' about the experience, which features on her new album 'Prism'. 

Talking to Entertainment Weekly, the hitmaker explained that it was cathartic to write and was important for her to get out into the open: "Well, imagine what you go through. Imagine what happens when you go through a break-up. We all go through break-ups and we all get very depressed and desperate."

"The lyrics are very exact and autobiographical. That's how I write. But the one thing about those lyrics is you can hear me finding my strength throughout the song. It starts off really low and then I kind of stand up for myself and say, 'No!'"

Perry added that it's about getting over feeling sorry for yourself and finding the inner strength that you had before everything went wrong: "Sometimes you look in the mirror when you're crying and if you look in the mirror it will make you cry more because you're feeling sorry for yourself." 

"And then sometimes you look in the mirror and you cry and I've been like, 'Snap out of it! It's time to - come on - grow up! No!' There's almost like this inner warfare that comes out, this inner battle between the good angel and the bad devil."