"She had to separate from him . . . to get ahead and focus on her career," the source explains. "He was in trouble then and she couldn't help him. A lot of her songs were partially inspired by him. I know 'The One That Got Away' and 'Circle the Drain' are partly about him, as well as Travis [McCoy of Gym Class Heroes]. But she was young and it was a time in her life she cherishes." (Perry became a worldwide pop star in 2008 with her smash, "I Kissed a Girl," and married Russell Brand in 2010. They finalized their divorce earlier this year.)
Adds the source, "They had good times. It's really sad. She could never help him and couldn't [let herself] go in that direction."