The latest entry in the series of memoirs from Back to The Future star Michael J. Fox reveals that his Parkinson’s diagnosis will take a further toll on his career, forcing him to retire from acting altogether.

Fox recently released his fourth memoir, No Time Like the Future: An Optimist Considers Mortality. The book details his planned retirement from acting due to the continuous strain that his 30-year battle with Parkinson’s disease has put on his health and memory. “There is a time for everything, and my time of putting in a twelve-hour workday, and memorizing seven pages of dialogue, is best behind me,” Fox writes. “At least for now … I enter a second retirement. That could change, because everything changes. But if this is the end of my acting career, so be it.”

Some of the recent symptoms Fox mentions are his declining memory and frequent confusion, such as speaking to individuals who are not in the same room. Fox mentions one incident where he confused one of his daughters for a different one. He also recounts suffering a fall not long after removing tumors from his spine.

His condition has begun to take a toll on his world-famous optimism.

“People have a lot worse than this to deal with, and I have a broken arm and a bad back and Parkinson’s and I’m whining and squealing and complaining,” Fox recounts. “So what good has optimism done me? And that began a kind of a semi-quasi journey to find my way back to being an optimistic person.”