"Today I'm going to work on my water machine to supply clean water to 4 billion people." Dean Kamen wouldn't be able to say that unless he happened to be an eternal optimist.
In an XPRIZE Insights video, Kamen says that most of the projects that he undertakes take many, many years to succeed. Therefore, you have to be an optimist to get up every morning and go at it again.
Watch the video here: