Nov. 16 (UPI) -- Michael J. Fox is looking back on how a "careless" accident led to his rock bottom moment.
The 59-year-old actor said on Monday's episode of Good Morning America that he blames himself for an "avoidable" health setback that caused him to question his optimism.
Fox also discusses his lowest moment in his memoir, No Time Like the Future: An Optimist Considers Mortality, slated for release Tuesday.
"It was definitely about a crucible that I went through in a really unlikely way," he said on GMA.
Fox was diagnosed with Parkinson's disease at age 29 in 1991 and said he'd reached a sort of "peace with it, kind of a détente" before his setback.
"It takes up the space it takes, and it left me room to do other things and thrive and golf and have friendships and travel," he said.
In 2018, Fox underwent an unrelated surgery to remove a noncancerous tumor from his spine. The surgery was successful but Fox had to learn to walk again following the procedure.
Fox was recovering when he ended up falling and breaking his arm while alone at his New York City apartment. On GMA, Fox said the accident set him off and was a personal "bottom."
"It was so useless. It was so pointless and so stupid, so avoidable," the star said. "I didn't do anything to cause Parkinson's. I didn't do anything to cause the tumor in my spine. But I did this."
"Everyone's taking an abundance of caution with me and warned me to be careful," he added. "I have to think before I walk; I can't just get up and go because I don't have much control of my momentum and control of my direction."
Fox previously said in the Nov. 16 issue of People that breaking his arm caused him to question "everything," including his optimism and his ability to offer hope to others.
On GMA, Fox said he was ultimately able to reclaim his positive outlook, and shared advice from his late father-in-law.
"He would always say, no matter what was going on, 'It gets better, kiddo. It gets better. The last thing you run out of is the future,'" he said. "He lived every day with gratitude and I realized, if there's gratitude, then you have sustained optimism."