John Stamos Admits He Was 'Shattered' After Rebecca Romijn Divorce: 'Maybe She Wasn't the Devil' (Exclusive)

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." He continues to explain that back then, "one of the steps in AA, the fourth step, is you lay out all your grievances, everything that people did to you. And then I said, 'Oh, she did this, she did that, blah, blah, she did blah, blah.' And then my sponsor goes, 'Now what part did you play in that?' And I go, like, 'None.'"

But the Big Shot actor eventually recognized he had "some part" in his first marriage's demise after his sponsor pressed him further. "You start thinking, it's like, 'Oh, she wasn't the Devil. Maybe I was as much to blame as her.'"

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."

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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.

"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.

For more on John Stamos, pick up the latest issue of PEOPLE, on newsstands everywhere Friday, or subscribe here.