This Founder Built a $1 Billion Brand ... By Giving Away $5 Gift Cards By getting scrappy, Grove Collaborative's Stuart Landesberg learned big lessons.

Stuart Landesberg started his career at Lehman Brothers and TPG Growth, but he felt a pull toward the sustainable-­living industry. He'd grown up composting in his family's backyard and had a vision of selling eco-friendly products online. "I was filled with the hubris of a 26-year-old guy who works in finance," he says.

So in 2012, he did what he thought he should: He looked for two cofounders, scrambled for meetings with investors, and showed off his grand plan for a company called ePantry. It would sell multiple existing brands. Nobody was interested. "It hurts me to even think about it," he says, laughing.

Those rejections turned out to be a great fortune, however -- ­because they forced him to be scrappy and inventive and understand his customer in perfect detail. His business transformed as a result. But of course, he didn't know that at the time. He was just trying to survive.