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Entrepreneurship, like any extreme career, changes you.

Exhibit A is Julia Hartz. As a former production developer and series manager for big-name TV shows such as Jack Ass, Rescue Me, and Nip/Tuck, the 34-year-old co-founder and president of Eventbrite has needed to duck and cover, as well as roll with the punches, more than she ever dreamed.

Hartz was just 25 when she launched the self-service online ticketing platform in 2006, with co-founder and now husband Kevin Hartz. The company makes money by charging 2.5 percent of the value of each ticket it helps sell, in addition to a 99 cent per ticket flat fee. Though the company refused to disclose its revenue for 2013, considering the number of tickets sold (60 million) and its gross receipts ($1 billion), Eventbrite reeled in a tidy sum of about $84.4 million in revenue for the year.

Fueling that growth, Eventbrite this year opened three new offices in Dublin, Nashville, and Melbourne, Australia. It also recently released a reserve seating option for ticket buyers. To date, the company has facilitated the sale of 200 million tickets to millions of events in more than 187 countries. 

But all this success has not come without significant change to both the company and Hartz personally. Thinking back on starting Eventbrite, Hartz says, her age didn't mean as much as her perspective. "I always considered myself a realist," she says. "And over the years, I've become more optimistic."

She credits her husband, who had previously founded the digital money-transfer company Xoom, with helping her shed her ever-pragmatic shackles. "Kevin has this eternal optimism that many entrepreneurs share," she says. That optimism helped persuade her to pursue the business to begin with, she says.

And though couples often cite relationship strain when they start up together, the Hartzes don't seem fazed. "It was clear to me that the two of them have a wonderful working relationship and a wonderful marriage," says Roelof Botha, director at the Menlo Park, California, venture capital firm Sequoia Capital. "That translated into the workplace," adds Botha, who is also an investor and a board member at Eventbrite.

Now 34, Hartz's adaptable personality became a crucial trait when, in 2011, she faced one of the defining moments in Eventbrite's history. At an opening-day brunch during South by Southwest, a call came in that caused Hartz and about 20 other staff members to drop their forks. "My phone started ringing. [Kevin's] phone started ringing, and all of a sudden I heard all of these vibrations throughout the room," she recalls. In that moment, Eventbrite was hosting one of its biggest events to date--Brooklyn, New York's Great GoogaMooga, a two-day food, wine, and music festival organized by the founders of Bonnaroo.

Though Eventbrite had practiced with simulations of the event webpage for weeks before the on-sale date, a minor tweak at the last minute caused a bug, and the whole page came crashing. "I'll never forget looking up at everybody in this restaurant and realizing that shit was hitting the fan," Hartz says.

Because most of Eventbrite's leaders were attending the event in Austin, far from company headquarters in San Francisco, they had to quickly find a place to huddle and address the crisis with no plan or clear direction. "Half of us ran across the street to the W, ran into this weird basement room, and set it up as our war room," Hartz says. "It was torture."

Yet the experience was also gratifying, she adds. The Eventbrite team got the site back up, and the event organizers still managed to attract more than 30,000 people. "It was unbelievable what happened," says Hartz. 

Despite Hartz's success, she still seems a bit shocked by it. "At Eventbrite, I'm used to operating on shifting tectonic plates and never knowing what the next day is going to bring," she says. "Eight years ago, if you were going to tell me that that was going to be my reality, I'd say no, thank you."