Christopher Reeve Allowed Himself 20 Minutes of Self-Pity Each Day After Accident (Exclusive)

After a fall from a horse left him paralyzed from the neck down in 1995, Superman actor Christopher Reeve's loved ones say the one thing he didn't do was give in to wallowing in self-pity.

According to the new documentary Super/Man: The Christopher Reeve Story (in select theaters Sept. 21 and Sept. 25), directors Ian Bonôte and Peter Ettedgui say the actor did his best to face each day with positivity, despite the challenges he faced all day, every day.

"He did allow himself 15 to 20 minutes of pity a day," director Ettedgui tells PEOPLE of what he learned about Reeve during the making of the movie.

"And that was it. Otherwise, it was like, there's not a single f---ing minute in the day to waste. He'd be thinking, 'I'm sad,' but then you could almost see him calculating like, 'That's it. Now it's time to get on with it.' "

The directors and Reeve's children credit the actor's wife Dana with helping him move forward after his spinal cord injury.

“My mom was maybe the most special person to ever grace this earth," says Will, 32, of Dana. "And it's a testament to her singular spirit that she lived every day by choosing hope. There was a relentless positivity that was not manufactured, it's just who she was. And it helped our family move forward."

He adds, "She was thrust into these unimaginable circumstances as a young woman, and my parents often joked, ‘We’re really testing that “in sickness and in health” part of our vows.’ "

Despite maintaining a positive attitude — and throwing himself into raising money for spinal cord injury research and making changes for the paralyzed community through the Christopher & Dana Reeve Foundation — the documentary doesn't gloss over how difficult life was afterward for the actor.

In the movie, which uses home video as well as footage from Matthew's earlier documentaries on his dad, you can hear Reeve talk about how he wanted to die in the days after learning he'd never walk again.

"I said, ‘Maybe we should let me go,’ ” Reeve said in archival footage. He said his wife replied, “I am only going to say this once: I will support whatever you want to do because this is your life and your decision. But I want you to know that I’ll be with you for the long haul, no matter what.”

He said she then said the words that saved his life: “You’re still you. And I love you.”

Reeve lived another 10 years after the accident, dying of heart failure at age 52 in 2004. In a cruel twist, Dana, a nonsmoker, would follow 17 months later from stage-4 lung cancer. The film also explores how Will, who was orphaned at 13, got by after losing his parents at such a young age.

“Grief is permanent," Will says. But he's proud of the work he and his siblings continue to do with the foundation, and loves watching his parents shine through Matthew and Alexandra, who are parents now themselves. He adds, "I think the most important element of the grief process is healing, and you can find healing by honoring people you’ve lost in the way we live our lives.”

The biggest lesson he says they learned from how Christopher and Dana lived their lives after the fall?

Will says, “We learned how important the family unit, and the love within a family, is to living a fulfilling and meaningful life."

For tickets to see Super/Man: The Christopher Reeve Story, visit Fathom Events.

To read more about Christopher Reeve's extraordinary life, pick up the latest issue of PEOPLE, on newsstands Friday.