The Roar hitmaker, who split from the British comedian in December 2011 after 14 months of marriage, admits she was so devastated by their break-up that she questioned whether she should "continue living".
The 28-year-old singer, who is now dating John Mayer, opens up about the split in the tracks Ghost and By The Grace of God on her upcoming album Prism, in which she sings: "Lay on the bathroom floor/Couldn't take it anymore/By the grace of God/I looked in the mirror and decided to stay/Wasn't gonna let love take me out/I thank my sister for keeping my head above the water/Every morning, I finally see myself again/Universe calling my bluff."
Katy told Billboard magazine: "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?'
"All the songs are real-life moments. 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 brunette beauty, whose new album will be released on October 18, recently sold the $6.5 million West Hollywood, California, marital home she shared with Russell.
The sale of the seven-bedroom and nine-bathroom home, which is based near the famous Sunset Strip, came after reports Katy slashed the price to attract a buyer.