ABC News' Lauren Sher and Alice Gomstyn:

Millions of people held their breath as daredevil Nik Wallenda walked his way into history, becoming the first person to traverse Niagara Falls on a high wire.

"It's exciting to know that I was part of history," Wallenda, 33, said, looking back on his stunning accomplishment Friday night. "What a blessing, the life that I've had so far. To be able to complete something that no one in the world ever has is quite an honor."

Wallenda crossed at about 200 feet in the air on a two-inch-wide wire strung over the raging waters of Horseshoe Falls, the largest of the three falls that make up Niagara Falls. Braving blinding winds and mist, the 1,500-foot walk took him a little more than 25 minutes to complete.

Although he called the journey "peaceful" and "relaxing," Wallenda said carrying the 40-pound balancing poll was more taxing than he expected and that his arms cramped up worse than ever before.

"It's a lot of forearm work and my forearm just started to cramp worse than it ever has been before. I don't know if it had to do with tension more than anything but it cramped up really bad," he said.

Of all the obstacles before him, the steps Wallenda took directly over the brink of the Falls were the most nerve-wracking, he said, and a test of true mental fortitude.

"Mentally, your mind goes, 'What are you doing?' That's where I tell myself you're on a wire. The wire is the same whether you're over land or over water or over the moon, it's still the same so focus on the wire and, again, focus on the other side," he said.

To keep that laser focus and stay centered, Wallenda turned to prayer.

"I really prayed non-stop," he said today on "Good Morning America." "The Bible says pray without ceasing and I'm always praying."

Within feet of the finish line on the Canadian side of the Falls, Wallenda pumped his fist in the air, dropped down to one knee and pointed to the crowd early awaiting his arrival before breaking into a big smile and taking his final steps across the wire.

"I'm grinning from ear to ear because I can see I'm here. I made it," he said.

Tens of thousands of people gathered at the falls, including his wife and family who waited to embrace him. After he greeted his loved ones, Wallenda was approached by customs agents, who asked him for his passport, which he presented.

"No, I'm not carrying anything over. I promise," said Wallenda, who used a tether to prevent his falling into the water.

"What is the purpose of your trip sir?" the agent asked.

"To inspire people around the world," Wallenda said.

Wallenda considered Friday's feat the fulfillment of a lifelong dream as well as a chance to honor his great-grandfather, legendary funambulist Karl Wallenda, who died after falling from a tightrope in Puerto Rico in 1978.

To the 13.1 million viewers who tuned in to see him walk into history, Wallenda hoped it served as inspiration to keep reaching forward and onward.

"I think that's what life is about. We all go through challenges. But once we get through them, we look back and say look how much our lives have changed by going through that challenge," Wallenda said. "If you can focus on the other side, when you look back it makes it that much easier."

How does Wallenda plan to top his latest feat? By walking across the Grand Canyon.

"No one in the world has ever done it and I already have the permits. It's about 5,000 feet long, almost a mile," he said.

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