From Larry Page’s 2012 update which is well worth a read:
When I was a student at the University of Michigan, I went on a summer leadership course. The slogan was “a healthy disregard for the impossible,” and it’s an idea that has stayed with me ever since. It may sound nuts, but I’ve found that it’s easier to make progress on mega-ambitious goals than on less risky projects. Few people are crazy enough to try, and the best people always want to work on the biggest challenges. We’ve also found that “failed” ambitious projects often yield other dividends. Believe it or not, the technological innovation behind AdSense, which, as I mentioned earlier, has paid out over $ 30 billion to partners, was the result of a “failed” more ambitious project to understand the Web. The team failed at understanding the Web, mostly, I think, because they were distracted by their work making advertisements amazingly relevant.
Last year, the Google+ team decided to integrate multi-person video into their efforts. They had a small committed team that was crazy enough to believe this was possible, and Google+ Hangouts was born. You can now video chat with anyone, anywhere, even from the Great Barrier Reef. It was the same with driverless cars, which we started on in 2008. Today we have driven over 200,000 miles, and Steve Mahan, who is legally blind, recently took a drive in one of them. So the one-sentence summary of how to change the world… work on something that is uncomfortably exciting!