Besides having a name which I have no idea how to pronounce, Mihaly Csikszentmihalyi, is the author of Flow, arguably one of the best and most recognized books in the field of positive psychology.
Mihaly, now 76 years-old, grew up in post-WWII Europe, and began to wonder how some people remained happy after so many of their villages and material belongings were left in ruins. This got him thinking about well-being and happiness, and he began studying creative people such as composers and how they felt when they were amidst the creative process. The rest is history.
He spoke at TED a few years back and discussed what makes a life worth living, and explained the concept of "flow" which he's become so famous for.
Here's the video: