Story highlights Felix Baumgartner has made more than 2,500 skydiving jumps

"Fear has become a friend of mine," he said

Baumgartner wore a pressured suit for a record-breaking jump, adding claustrophobia

Of all the things Felix Baumgartner had to worry about while pursuing his dream of skydiving from 120,000 feet, the one that almost stopped him cold was ...

Claustrophobia.

"Fearless Felix" got a bit freaked out by the pressurized suit he'll wear during his ascent and, more importantly, his supersonic descent from 23 miles up -- now tentatively scheduled for Sunday or Monday. Getting over his discomfort was a key hurdle to clear as the Austrian adventurer set out to make the highest skydive ever.

To that end, Red Bull, his sponsor, called in Dr. Michael Gervais. He's a sports psychologist who specializes in high-performance and "extreme" sports like, say, falling out of the sky at the speed of sound. Red Bull wanted him to psychologically evaluate Baumgartner and help him conquer his fear.

It must be said that Baumgartner is no stranger to fear or death-defying situations. The 43-year-old former military parachutist has made more than 2,500 jumps, including dives from the Petronas Towers and the Taipei 101 skyscraper. Clearly he has learned how to put aside fear, even use it to his advantage.

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"Fear has become a friend of mine," he said in a statement. "It's what prevents me from stepping too far over the line. On a mission like this, you need to be mentally fit and have total control over what you do, and I'm preparing very thoroughly."

But his plan to break the unofficial record retired Col. Joe Kittinger set with a leap from 102,800 feet in 1960 revealed a fear Baumgartner hadn't felt before. And it had nothing to do with coming down from such a height, but suiting up to reach it.

To prevent a potentially fatal condition called ebullism, Baumgartner must wear a custom-made space suit and helmet. Although the suit, based on those worn by high-altitude reconnaissance pilots, is designed to maximize maneuverability and visibility, it constricts his movement and vision. He'd never worn a pressurized space suit before, and he felt the claustrophobia — which, according to a New York Times account , was so severe it brought on panic attacks — threatened to bring the mission to a screeching halt.

That's when Gervais stepped in. After determining that Baumgartner was entirely committed to making the jump and not using claustrophobia as an excuse to back out, he set to work. (Baumgartner, who is in Roswell, New Mexico preparing for Sunday's launch, could not be reached for comment, but Red Bull confirmed Gervais' account for Wired.)

Over the course of three days, Gervais determined Baumgartner didn't have quite the right tools to manage his mind and emotions in the face of so great a risk. That's where the suit became an issue: It was a symbol of his not having complete control of the situation. To combat this, Gervais said, Baumgartner had to reconnect with his vision. He'd become too focused on the suit, not the goal he hoped to reach wearing it.

Simply put, he needed to get his eyes back on the prize.

"When we are in a high stakes or intense situation, it's not uncommon for our minds to jump forward, going to the next moment and worrying about what happens when this moment doesn't go well," Gervais said. "What happens is we give 50 percent to something that doesn't exist yet and 50 to this moment."

To reconnect with his vision, Baumgartner needed to reconnect to what Gervais called his hidden journey — what the jump meant to him, beyond being the first person to skydive from so great a height, or being the first person to exceed the speed of sound (about 700 mph at that altitude) in free fall. The hidden journey, he said, is much more basic: Baumgartner wants to go somewhere no one has ever been.

Gervais taught Baumgartner how to better manage his mind and body under pressure. Baumgartner mastered something Gervais called "combat breathing," or deep breathing, to calm himself. And he developed positive self-talk, using great care in choosing the words he used when talking to himself and others about the jump.

"Self-talk is considered one of the most powerful mental skills," Gervais said. "Self talk is the foundation for self-confidence and self-esteem."

To sharpen these skills, Gervais put Baumgartner in increasingly uncomfortable situations — which he would not specify — and made him try to gain control of his body and mind.

"We cultivated a situation to move a person to the edge of panic," said Gervais. "Imagine doing that repeatedly over 30 hours of training and at the end of it, you've got full control of how your mind works, and you breathe freely in those moments."

To further help Baumgartner, Kittinger — a trusted adviser who has worked closely will Baumgartner over the years — will be the only voice the Austrian will hear on the radio.

"Felix trusts me because I know what he's going through — and I'm the only one who knows what he's going through," the retired colonel told the Times. His flight team also devised a detailed pre-launch procedure to help occupy Baumgartner's mind before lift-off.

Once Baumgartner's mind was at ease, Gervais had to convince the Stratos team the problem had been solved. Because his ascent, in a space capsule dangling beneath a 55-story helium balloon, would take about 3.5 hours, and the descent about 20 minutes, he had to demonstrate 4.5 to five hours of proficiency in the suit.

"Then they would feel comfortable that Felix as a man and an athlete could manage himself in a space where no one else has been," Gervais said.

We already know Baumgartner passed the test, because he made successful test jumps from 13 miles up in March and 18 miles up in July. That said, the repeated weather delays — the jump has been twice delayed by high wind — can't be helping the mental strain, but Gervais is confident that Baumgartner has what it takes to stay focused on the task at hand.

"He's somebody that is willing to commit everything to his vision," added Gervais. "Everything is on the line. It's a great emblem for all of us to find value and fully commit to a vision."