The daredevil is youthful and athletic, solidly built from gym workouts and a lifetime of training. But it's the mental element, trusting in his skill and tuning out the potential danger, that can mean the difference between success and failure.
"You can either talk yourself out of doing something or you can talk yourself into doing something," he said.
Since first stepping on a wire when he was 2, Wallenda, who lives in Sarasota, Fla., has earned six Guinness records. His family has been performing for audiences at circus-style shows for more than 200 years.
The Niagara Falls walk set for Friday night, above a nearly 200-foot drop and through potentially high winds and vision-obscuring mist, will be unlike anything he's ever done. Because it's over water, the 2-inch wire won't have the usual stabilizer cables to keep it from swinging. Pendulum anchors are designed to keep it from twisting under his elkskin-soled shoes on the 1,800-foot walk from the U.S. shore to Canada.
"The thing about this cable, it's unique to me even, and because of that I'll be very, very focused on it," he said.
A born-again Christian, Wallenda said he stays calm on the wire by talking to God, quoting scripture and praying. He also stays in touch with his father and chief rigging engineer, Terry Troffer, through an earpiece.
And unlike his usual antics Wallenda's been known to make phone calls and lie down on the wire mid-walk he may be more inclined to get from one side to the other as quickly as possible, a request from his 11-year-old son.
"You can tell he is a little bit nervous about it," said Wallenda, whose three children are normally so comfortable with what he does that he once spied his two boys playing Nintendo games while he walked 200 feet above them over the Allegheny River in Pittsburgh. Wallenda's acrobat wife, Erendira, traces her own circus blood eight generations deep on her mother's side and seven on her father's.
"I always give (the kids) a hug and a kiss before I do anything," said Wallenda, "but they're used to it in a lot of ways."
About a dozen other tightrope artists have crossed the Niagara Gorge downstream, dating to Jean Francois Gravelet, aka The Great Blondin, in 1859. But no one has walked directly over the falls and authorities haven't allowed any tightrope acts in the area since 1896. It took Wallenda two years to persuade U.S. and Canadian authorities to allow it.
That it will be a Wallenda attempting the history-making walk only adds to the allure.
The Wallendas, the first family of the high wire, trace their fearless roots to 1780 Austria-Hungary, when ancestors traveled as a band of acrobats, aerialists, jugglers, animal trainers and a bit later, trapeze artists. The family has been touched by tragedy: Notably, Nik's great-grandfather and the family patriarch, Karl Wallenda, fell to his death during a walk in 1978 in Puerto Rico.
"I am carrying on the legacy and that does put a lot of weight on my shoulders," Wallenda acknowledged, "but in no way have my parents or grandparents ever said, 'Well, you need to do something bigger or better.'
"It's kind of built into me," he said, often quoting Karl Wallenda's mantra: "Never give up."
Another son of a daredevil legend understands that drive. "Kaptain" Robbie Knievel, the now 50-year-old son of the late Evel Knievel, has been making dangerous motorcycle jumps since he was 8, and isn't done yet. He made up his mind as a child that he'd continue his father's legacy and remains committed today.
"It's something I want to do, carry on the name, the tradition," he said by phone from his Las Vegas home, "to keep the name Knievel the most famous on two wheels. It's just something I grew up with and knew I wanted to do."
It was his own father's friendship with Karl Wallenda that steered Evel Knievel into performing.
"I'm a dying breed," the son said. "And Wallenda's a dying breed."
Wallenda will have one safeguard, a tether that will keep him out of the water if he falls, but not on the wire. ABC, which is televising the walk, insisted on it. Wallenda said he only agreed because he's not willing to lose this chance and needs ABC's sponsorship to help offset some of the $1.3 million cost of the spectacle.
"This is what we do. I feel like that's taking away from it," Wallenda said. "I feel like I'm cheating at that point."
The tether is another obstacle to contend with in a family whose shunning of safety devices is part of the appeal of the act.
"Life," he said, again quoting his great-grandfather, "is on the wire. Everything else is just waiting."