Emmett Shear, the quirky and focused and highly successful CEO of Amazon-owned streaming phenom Twitch, knows the exact moment he went from being a failing entrepreneur to the leader of a high-growth business.

Justin.tv, Twitch’s predecessor company, was a well-before-its-time 24-hour reality TV webcaster. It wasn’t working. Shear and his partners decided to focus on just one kind of streaming product, on the conviction that simplicity would give the startup a fighting chance. The company could have gone in multiple directions, including sports. But Shear, a bonkers online gamer, knew how he was spending his own time on the service, and so Twitch was reborn with an emphasis on gaming.

By 2014, Amazon bought Twitch for nearly $1 billion. Shear continues to run the company, safe inside Amazon (AMZN) but independent in its operations.

The great thing about this story, which Shear told at a Brainstorm Tech warm-up event in San Francisco Tuesday night, is how he came to the right decision. He didn’t follow the advice of consultants. He didn’t follow a fad he’d read about in a business book. He didn’t throw proverbial spaghetti against the wall to see what would stick.

He went with what he knew–with the knowledge that it might not work, but the confidence that he wanted to buy the product he planned to sell. It’s a good lesson for entrepreneurs on up to managers of giant businesses.