WATCH Katy Perry 'Prism' New Song 'By the Grace of God' Debuts at iTunes Festival in London: Heartbreaking Ballad Addresses Suicidal Thoughts Following Russell Brand Divorce [VIDEO]

Katy Perry has debuted a new song from her upcoming album "Prism," and this one is a doozy. At the iTunes Festival in London yesterday (Sept. 30), Perry premiered the heartbreaking, revealing ballad "By the Grace of God" just three weeks before her new album's release date.

The personal anthem was inspired by Perry's divorce from comedian Russell Brand in 2011. According to her cover story in Billboard, the impact of the divorce led Perry to a dark place, contemplating suicide on a bathroom floor. "By the Grace of God" addresses those moments.

"That song is evident of how tough it really was at a certain point. I asked myself, 'Do I want to endure? Should I continue living?'" she said. "I can only write autobiographically. I put all the evidence in the music. I tell my fans if they want to know the real truth about stuff, just listen to the songs."

The dark times are clearly evident in the song's lyrics. "Thought I wasn't enough / Found I wasn't so tough / Laying on the bathroom floor / We were living on a fault line / And I felt the fault was all mine / Couldn't take it anymore," she sings over a stripped down, simplistic piano melody.

Watch Perry's performance of "By the Grace of God" below.

"By the Grace of God" is the fourth songs fans have heard from "Prism." The album is led by the No. 1 single "Roar," and Perry has also released "Dark Horse" (featuring Juicy J) and "Walking on Air" in full as teasers for the album.

Katy Perry's third studio album "Prism" will be released Oct. 22.