By MEGAN STONE, ABC News

(NEW YORK) — Actor Michael J. Fox, who first announced he had Parkinson’s in 1998, opened up about his illness and the challenges he’s facing.

In an interview with People magazine, the Back to the Future star revealed that the disease is starting to infringe on his ability to act.

“My short-term memory is shot,” he said.

“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,” the Emmy Award-winner, who isn’t sure if he’ll return to acting, said.

Parkinson’s disease is a nervous system disorder that impacts movement, according to the Mayo Clinic. There is no known cause, and complications can include cognitive challenges, issues with swallowing and sleep disorders.

Despite his diagnosis, the Designated Survivor alum refuses to slow down. He’s focusing his creativity on writing and, already, has published three books. His fourth, No Time Like the Future, is due out Nov. 17.

“My guitar playing is no good. My sketching is no good anymore, my dancing never was good, and acting is getting tougher to do. So it’s down to writing,” Fox joked. “Luckily, I really enjoy it.”

The Golden Globe winner also said that he is always optimistic about the future, telling People, “Optimism is sustainable when you keep coming back to gratitude, and what follows from that is acceptance.”

“Accepting that this thing has happened, and you accept it for what it is,” Fox continued. “It doesn’t mean that you can’t endeavor to change. It doesn’t mean you have to accept it as a punishment or a penance, but just put it in its proper place. Then see how much the rest of your life you have to thrive in, and then you can move on.”

Fox, who turns 60 next summer, added that his optimism delivered him “through the darkest times.”

“Life is rich. Life is good,” he concluded.

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