In 1978, when I was 18 and she was 28, Diana Nyad first attempted to swim from Cuba to the Florida Keys. I read about her at the time with fascination--she was fairly well known in Manhattan, where I grew up, for her record-setting swim around the island in just over eight hours. I was rooting for her on that first Cuba-to-Florida attempt and sad when her medical team pulled her from the water after rough swells buffeted her.

She tried it again in August 2011, then again the following month, and yet a fourth time in August 2012. Each time she was stopped by jellyfish stings, sometimes combined with storms. When I heard she was trying it yet again last week, I was decidedly skeptical. "Isn't it time she faced reality?" I asked. "Enough is enough."

Boy was I wrong. Around 2 p.m. on Labor Day she walked out of the water in Key West, having finally finished the swim, 35 years after she first tried it and just 12 days past her 64th birthday. Wavering on her feet, slurring her words, and about to be carried off by stretcher, she nonetheless summoned the energy to deliver an important lesson to the hundreds of people standing on the beach and the millions more watching by video. "I got three messages," she began:

"One is, we should never, ever give up."

On three of her previous tries she suffered through box jellyfish stings so debilitating they're known to bring Navy SEALs low. "I feel like boiling hot oil I've been dipped in, and I'm yelling 'Fire! Fire! Fire!'" Nyad recalled.

Would you jump back in the water, knowing those things were in there? I sure wouldn't, but she did, again and again. Is there anything you want in this life so badly that you'd deliberately face that kind of pain? If there is, chances are you're going to get it.

"Two is, you're never to old to chase your dream."

"A couple of years ago I was turning 60, and I don't like being 60," she said in a 2011 TED talk. "How could this have gone by like lightning? I couldn't forgive myself for the countless, countless hours I had lost in negative thought."

Then her mother died at 82, and Nyad suddenly felt not only unsatisfied about the past, but also a keen sense that the future was finite. The answer, she decided, was to throw herself into an all-consuming dream, one that had been nagging her since she first failed to make the crossing in her 20s. She hadn't swum, she said, in 31 years, but she was prepared to put everything on the line to make that long-term dream a reality. "We blink and another decade passes," she told a live chat audience that same year. She wasn't willing to reach the end of her life and regret not giving it her all. And so she started to train.

What might you regret not having done, when you reach the end of your own life? And what's stopping you from starting on whatever that is right now?

"Three is, it looks like a solitary sport, but it's a team."

Having the right people to back her up was what finally made the difference. Nyad brought in jellyfish experts and following their advice, she spent nights swimming in a special suit that covered her arms and legs, spread with "sting stopper" gel. Perhaps even more important, she had shark divers on her team who chased away sharks and jellyfish before she ran into them.

The lesson is clear: If you want to do something extraordinary, you need extraordinary people working with you. And you should never be afraid to ask for help.

"I can swim from Cuba to Florida. And I will swim from Cuba to Florida."

Nyad made this simple declarative statement near the end of her TED speech. She'd tried and failed to do exactly that the previous the month, and the month before. Yet her calm confidence that it could be done and that she would do it was unswerving.

Anyone who's ever approached a project or a challenge with that kind of absolute certainty can attest to its effect, both on the people who work with you, and on the universe at large--things seem to just fall into place. That's what happened for Nyad on her final attempt. Sharks stayed away and there were fewer jellyfish than usual. There was only one brief storm, and even the current helped her along, bringing her in to Key West a bit earlier than planned.

Thanks to Diana Nyad for the inspiration her perserverence provides. Yes, we should never, ever give up. And we should never doubt that we'll accomplish what we set out to do.