John Stamos never envisioned his marriage to Rebecca Romijn would implode the way it did.

In his upcoming memoir, If You Would Have Told Me, out Oct. 24, the Full House alum candidly shares the ups and downs of his love story with Romijn, 50, along with the aftermath of their early 2000s divorce.

“My first marriage was shattering to me. I was shattered for way too long, too,” Stamos, 60, exclusively tells PEOPLE in this week’s issue. “I mean, a year, okay, good. But it went on [for] years and years.”

Stamos says it was “really difficult” to write the chapters centered around the pair’s former marriage, especially as he had to reflect on his feelings at the time.

“In my mind back then, she was the Devil, and I just hated her,” he admits. “I couldn’t believe how much I hated her, and it ruined my life. Looking back, and I talk about it [in the book], because it’s one of the steps in AA where the fourth step is you lay out all your grievances, everything that people did to you. I go like, ‘None.'”

But the Big Shot actor eventually recognized he had “some part” in his first marriage’s demise, saying, “You start thinking, it’s like, ‘Oh, she wasn’t the Devil. Maybe I was as much to blame as her.'” (L-R) Rebecca Romijn and John Stamos are pictured. Paul Archuleta/Getty, Allen Berezovsky/FilmMagic

From his perspective, Stamos — who hasn’t seen Romijn since their joint meeting with their divorce attorneys — felt his now ex-wife “was trying to make it work because she cared” about him before they eventually split.

“It was very public, and that was very painful. I didn’t write much about that, but it’s hard,” he says.

“It was very much the opinion that she dumped me because her career was going great and mine wasn’t, and that’s humiliating,” he continues. “I don’t blame her for it. It was just the perception that people took, and maybe they weren’t wrong. She was doing great at that time and I wasn’t.”

Stamos feels his healing process “was not healthy.”

“That’s when I really started to kind of drink a lot,” he recalls. “But without that, I never would’ve known what a real love is, and I would’ve never straightened up to get someone like Caitlin in my life.”

Stamos married Caitlin McHugh Stamos in 2018. They are now parents to 5-year-old son Billy. Meanwhile, Romijn now shares two children with now-husband Jerry O’Connell, whom she wed in 2007. (L-R) John Stamos, Billy Stamos and Caitlin McHugh Stamos are pictured.

John Stamos/Instagram

“If I didn’t go through all the things, all the heartache,” the Scream Queens alum says, “I wouldn’t be who I am today. That’s what I hope people take away from it.”

John Stamos’ memoir, If You Would Have Told Me, is available Oct. 24 wherever books are sold.