03/15/2013 AT 11:15 AM EDT
On Feb. 11, two days before Carrie Fisher boarded ship as a headliner for a gay cruise in the Caribbean, she had a nightmare: An armed militia lay in wait on the boat, and in the dream she warned her assistant, "You don't have to go, but I do!"
Despite that premonition, they set sail from Aruba, Fisher's bulldog Gary in tow. "It was whatever pathetic thing I picked up from my mother [Debbie Reynolds]," says Fisher. "You know, the show must go on."
Unfortunately, it did. By the time Fisher took the stage, the 56-year-old bestselling author, screenwriter and Star Wars actress was in the throes of a bipolar episode. Shocked audience members watched as she rambled, slurred words and mumbled lyrics. Her dog relieved himself onstage as some people fled.
"I went completely off the rails," says Fisher, who wrote about her mental illness and prescription drug addiction in her 2008 memoir
Wishful Drinking, also a hit one-woman show. When video of the incident hit YouTube about a week later amid speculation Fisher had fallen off the wagon, her rep issued a statement explaining she'd had "a medical incident related to [her] bipolar disorder" and had gone to a hospital to reevaluate her meds. Still recovering at home in Los Angeles, an upbeat and wry Fisher exclusively opened up to PEOPLE's Elizabeth Leonard about how the chaos onstage was nothing compared to the bedlam swirling in her head.
I don't really remember what I did. I haven't watched the videos that people took. I know it got bad. I was in a very severe manic state, which bordered on psychosis. Certainly delusional. I wasn't clear what was going on. I was just trying to survive. There are different versions of a manic state, and normally they're not as extreme as this became. I've only had this happen one other time, 15years ago, so I didn't have a plan of action. That time I was in a [psychiatric] hospital, and I was being talked to by the television, hallucinating. I wasn't inside the TV this time, thank God. [But] I was in big trouble.
[On the cruise] I wasn't sleeping. I was writing on everything. I was writing in books; I would have written on walls. I literally would bend over and be writing on the ground and [my assistant] would try to talk to me, and I would be unable to respond. That was what I spent my teenage years doing: handwrite, handwrite, handwrite to the point where I'm running out of ink. I can't wait to see what I wrote. I don't know what the hell it says. I do know this – and it was really bizarre – I was trapped in a metaphor. Everything I looked at had a meaning. Everything was a warning or a sign. I was in a part of my brain I've only been in one time before.