Looking back on your past isn't always an easy thing to do, which is why Tom Petty waited this long to open up about his heroin addiction.

In the iconic musician's new biography, readers will learn all about his struggle in the '90s, which is a topic he chose to keep out of the spotlight until now, according to Ultimate Classic Rock. "Petty: The Biography" is written by Warren Zanes, who was a part of the band the Del Fuegos, and will be released on Nov. 10. While it is all about Petty's life, the 64-year-old singer/songwriter pretty much just endorses it, so he gave Zanes free reign to write whatever he wanted.

"He didn't want to be authorized, because he felt like authorized meant bulls--t," Zanes told The Washington Post. "He said, 'I want it to be yours. And I can't tell you what you can and can't write.'"

This allowed Zanes to reveal Petty's heroin addiction to the world, and while Petty was a little hesitant at first, Zanes assured him that it would be OK.

"The first thing [Petty] said to me on the subject is, 'I am very concerned that talking about this is putting a bad example out there for young people. If anyone is going to think heroin is an option because they know my story of using heroin, I can't do this,'" Zanes continued. "And I just had to work with him and say, 'I think you're going to come off as a cautionary tale rather than a romantic tale.'"

The addiction took place when Petty was in his 40s and 50s, during a time when he was a true "rock and roller" and was constantly hanging out with people who were also doing it. "That happens when the pain becomes too much and you live in a world, in a culture, where people have reached in the direction of heroin to stop the pain," Zanes said. "He hit a point in his life when he did not know what to do with the pain he was feeling."

In the biography, Petty then speaks about what it was like trying to mask the pain he was feeling. "I probably spent a month not getting out of bed, just waking up and going, 'Oh f--k,'" Petty says in the book, according to Entertainment Weekly. "The only thing that stopped the pain was drugs. But it was stupid. I'd never come up against anything that wasn't bigger than me, something that I couldn't control. But it starts ruining your life...I'm lucky I came through. Not everyone does."

As for why he waited this long to talk about it, and what pain he was really trying to fix, Zanes isn't really sure. He believes it had something to do with his divorce from his first wife Jane Benyo or the fact that his band mate Howie Epstein was also an addict who eventually died from a heroin overdose. Back in 2007, during his documentary "Runnin' Down a Dream," Petty had plans to share this with the world but had a change of heart and cut the scenes that spoke about his addiction. Zanes said his addiction was "the classic situation of midlife pinning a person down to the mat."

Read the full interview with Zanes here.