Michael J. Fox does not look back wistfully at his pre-Parkinson's disease days, when he starred in the TV shows "Family Ties" and "Spin City" and the "Back to the Future" movies.
Sometimes when he catches himself on TV, he'll stop to watch for a few minutes.
"There's no longing in it. There's no… this deep feeling of loss or anything," Fox told "Good Morning America's" Diane Sawyer today. "It's just like, acknowledgement that that was part of what brought me to where I am now, and it was pretty fun."
The title of Fox's new book, "Always Looking Up: The Adventures of an Incurable Optimist," is a joke about his 5-foot, 4-inch stature. But optimism isn't just a way of life for the Emmy-winning actor, it's a forceful weapon in his fight for a Parkinson's cure.
After his emotional goodbye from "Spin City" 10 years ago, Fox put his acting career on the back seat to push the Michael J. Fox Foundation, which has provided millions of dollars to help researchers find a cure for Parkinson's.
On Tuesday, Fox takes on his most extensive acting turn in years. He'll join the cast of the F/X TV show "Rescue Me," playing a pill-popping, quadriplegic paramour of Denis Leary's character's ex-wife.
Fox is not only optimistic but full of jokes about his condition and making the most of what life hands you.
Brushing his teeth, he said, is "like having an electric toothbrush without the battery."
"Then it's kinda like, you know, 'West Side Story.' It's kinda like Sharks and the Jets. I have to wrestle ... the knife outta my hand and get the brush down into the basin," he said.
Fox and his wife, Tracy Pollan, have been married for a little more than 20 years. They married in 1988 and two years later, Fox began developing early onset symptoms of Parkinson's disease.
Fox called Pollan "a spectacular ... friend and partner and companion. ... Just the yin to my yang, whatever that means."
A key to their successful relationship? "Keep the fights clean and the sex dirty. And ... just, have fun."
The couple has four children -- Sam, 20, and in college; 14-year-old twins Aquinnah and Schuyler; and 7-year-old Esmé.
Fox said mornings are his most difficult time of day. When he wakes up, he can't go back to sleep because the Parkinson's effects cause his body to start moving and he experiences painful foot cramps.
But his favorite time is at the end of the day. "When everybody kind of gets back home and the kids come home from their days and there's just bedlam at dinnertime and homework and you know, 'Where ...where's my math book,' and, you know, 'I want a hamster.'"
Fox once called Parkinson's a "gift," which angered some people with the disease. So he amended his statement, saying, "OK, if it's a gift, it's a gift that keeps on taking. I'll give you that."
But he does believe that having the disease has provided him with some irreplaceable experiences -- meeting new people, writing the book, even playing "Magic Bus" live with The Who.
In a 2000 interview with "20/20," Fox said that he firmly believed there would be a cure for Parkinson's disease by the time he was 50 years old. He is now 47 and remains positive that a cure will come soon, perhaps not in three years, but soon.
On March 9, President Obama lifted a ban on federal financing for embryonic stem cell research, which has shown promise for curing diseases such as Parkinson's.