“Back to the Future” star Michael J. Fox is opening up about an accident he suffered in 2018 that he refers to as the “darkest moment” of his life.

Fox’s new memoir, “No Time Like The Future,” hits shelves Nov. 17 and recalls the incident that occurred just a few months after the 59-year-old actor underwent spinal surgery to remove a potentially paralyzing tumor. Following the surgery, Fox endured four months of intense recovery that included relearning how to walk, according to TODAY.

Figuring the worst was behind him, the actor spent a weekend with his family on Martha’s Vineyard and then returned to his New York City apartment to film a cameo in a Spike Lee movie, according to People. On the morning of the shoot, Fox slipped and fell in the kitchen. The fall shattered the actor’s arm, and in that moment, he said he felt an overwhelming feeling of despair.

“That was definitely my darkest moment,” said the actor — who went public with his Parkinson’s diagnosis in 1998 — during an interview with TODAY. “I just snapped. I was leaning against the wall in my kitchen, waiting for the ambulance to come, and I felt like, ‘This is as low as it gets for me.’ It was when I questioned everything. Like, ‘I can’t put a shiny face on this. There’s no bright side to this, no upside. This is just all regret and pain.’”

Fox also revealed that his Parkinson’s symptoms have extended beyond his speech and motor skills and are now affecting his memory.

“My short-term memory is shot,” the actor told TODAY. “I always had a real proficiency for lines and memorization. And I had some extreme situations where the last couple of jobs I did were actually really word-heavy parts. I struggled during both of them.”

According to People, during this period, Fox struggled to tap into the optimism that was usually so present in his thoughts. The actor began to doubt his abilities to offer hope to others.

“How can I tell people, ‘Chin up. Look at the bright side. Things are going to be great?’” he recalled thinking.

Eventually, with the help of his family and old TV reruns, the actor was able to adjust his outlook and rediscover the optimism that had buoyed him for years, People reported.

“Optimism is really rooted in gratitude,” the actor told TODAY. “Optimism is sustainable when you keep coming back to gratitude, and what follows from that is acceptance. ... It’s not that I wasn’t sincere before, but my gratitude is deeper now, from having gotten through the darkest times.”