Too Good To Go CEO Mette Lykke’s first step to meteoric success didn’t involve anything as thought-out as a business plan or a problem she wanted to solve. It was much more elemental.

“It started with the decision to quit and build something,” Lykke says of the first moment of her journey.

Prior to becoming chief of the sustainable food app that is saving 80 million meals a year from going to waste, she was co-founder and CEO of Endomondo, the fitness app that she eventually sold to Under Armour for $85 million in 2015.

But before that, Lykke was simply a McKinsey consultant who wanted nothing more than to be an entrepreneur. The Danish self-starter didn’t have a business plan or an outlandish idea, just the knowledge that she wanted to have an impact on the world and “see something grow from A to Z”.

So she convinced two McKinsey work friends who joined on the same day to throw in the towel on their consultancy careers and team up to launch a business together—and that’s exactly what they did in 2007.

“And then we had to come up with something,” she tells Fortune with a hint of humor.

After quitting their jobs, Lykke and her former McKinsey peers came up with a list of 10 start-up ideas before settling on creating a fitness community app based on free real-time GPS tracking of running, cycling, and other distance-based sports. They called the venture Endomondo, and the rest is history.

“A lot of aspiring entrepreneurs are just sitting there in their corporate jobs waiting for that lightning moment when they have the great idea,” she adds. Then she adds a warning: “It’s not going to land in your lap, you just decide to go for it or you don’t. Once you decide to go for it, you will come up with something because you have to.”

$100,000 is a cheap price to chase your dreams

Although she and her co-founders took a very “McKinsey approach” to founding the business—including scoring each potential idea on its product-market fit and their existing network in that industry—which give it a better chance of success, no startup is entirely foolproof.

Yet Lykke didn’t have a backup plan. Contrary to common advice, she put all her eggs in one basket.

Looking back, even if the venture had failed, as many do in the first few years of inception, Lykke still thinks quitting your career and taking a leap of faith is worth the risk—especially when you’re young, childless and mortgage-free.

“The worst thing that can happen is that it’s not going to work out, you’re going to lose whatever money you invested, and you’re going to go a couple of months without any employment,” she said. “If you think about it from that perspective, if it’s going to cost $10,000 or even $100,000, to pursue your dream, I actually think that’s pretty cheap,” she says.

It’s a far better fate, in her eyes, than always asking yourself, what if? “It’s like, okay, but at least you really had a go at it,” she adds.

Lykke’s advice for those who are dreaming about their passion project from their desks is to be brutally honest with yourself about the potential fallout from giving up your day job to chase your aspirations—and failing.

“For me, I had McKinsey on my CV and pretty good results from university. I was fairly employable so I was quite sure if this didn’t work out, I could probably find a job somewhere,” Lykke says. But, that’s not the case for everyone.

We couldn’t afford a CEO—so I took the job

For most CEOs, their climb up the ladder to the top role is meticulously planned—often with the help of a career coach. But for Lykke, her foray into leadership was completely unexpected—unwanted, even.

When her co-founder Christian Birk stepped down as CEO five years after launching Endomondo, Lykke, who was then in charge of “everything marketing related” as its CMO, began the process of finding his successor.

“I was quite convinced that I didn’t have the skills that it was going to take,” she admits. But after searching for the perfect external candidate, it wasn’t long before Lykke realised that the business couldn’t afford to hire the calibre of chief executives that she was interviewing.

“The company wasn’t doing super well and all those who were qualified were too expensive for us,” she recalls.

After feeling deflated about the entire situation, Lykke’s dad offered her a reality check: “I’m sorry to say, but it sounds like you have to do it yourself,” he matter-of-factly told her.

So she rolled up her sleeves and begrudgingly took the helm in January 2012—but not without the help of her workforce. “I definitely knew that there were some things that I had to work on personally so I also invited our team to give me feedback on what those points were—which they did, painfully,” she says.

Much of the criticism she received was based on the working style that she had picked up in her consulting days, like expecting people to be “self-motivated and get stuff done”.

“It wasn’t the most inspiring way of leading people—they told me that in so many words,” she adds. “I also just needed to build a little bit more understanding around the fact that, while this was my everything, other people actually had a life on the side that they would like to sustain.”

Although leadership didn’t come naturally to Lykke, by fine-tuning her soft skills she became a well-rounded force to be reckoned with. Not only was she now able to motivate her workers, but she could also lean on her marketing background to grow the app’s user base to 20 million and prime the company for sale.

“Good leadership is not something you’re born with, it takes training and coaching,” Lykke advises.

You never know where your next paycheck—or CEO proposition—will come from

After Endomondo’s acquisition in 2015, Lykke, in her true style, wasn’t planning her next move.

Rather than enlisting the help of a headhunter to find her another leadership role, a leadership role found its way to Lykke in the most unlikely of places: While on a bus in Copenhagen, she first caught a whiff of a brand-new food platform, Too Good To Go. “The woman next to me showed me the app on her phone and it turned out she was an angel investor,” Lykke says.

The serendipitous encounter led to an introduction with the 8-month-old start-up’s five founders, who were looking for funding and advice from a seasoned app builder. “I offered both,” Lykke says while adding that within a few weeks they asked if she would consider becoming its CEO.

“To put aside ego and say, someone else may be better able to drive this forward is hard,” she recalls. “This time, I definitely felt ready.”

On paper, it was a step down from running Endomondo’s large team at Under Armour as its VP. “But again, it comes back to me not really having a career plan,” she says.

“I don’t care a ton about titles, our team size or stuff like that,” she adds. “I really care about having an impact and I’m happy to put in hard work whenever that’s required—but I want to know that it actually makes a difference.”

Since taking its helm, she’s grown Too Good to Go from the ground up to a team of around 1,200 people spanning 17 countries; 145,000 stores now sell their unsold food on the app to over 80 million customers. Last year, it was the fastest-growing sustainable food app in terms of downloads, with 9.8 million new sign-ups on Android devices alone.

And make a difference it has: The app saves three meals from going to waste every second, 24/7. Still, Lykke says her work is far from over.

“I’m not someone who will ever feel like, now I’m content—my job is done. There’s so much more to do, 80,000 meals are wasted every second. The issue is massive,” she reflects. “It’s great that we saved three of them. But there’s still 80,000 out there.”