In that most important tome of positive psychology, Flow: The Psychology of Optimal Experience, Mihalyi talks about how athletes get "in the zone" or when workers "lose themselves" into their work. This is being in "flow" and Mihalyi argues that it's possible to live everyday in flow. The idea is to achieve the appropriate balance between challenge and skills. This graphic is key:

In the later chapters, Mihaly extends the concept of flow to the rest of our lives, and believes that happiness comes from leading an entire life in flow. To understand this requires looking at the graphic a little differently:

You know that saying, "follow your fears"? I think that's precisely what this is talking about. While you may be challenging yourself everyday at work (I know I am), if your career as a whole isn't a challenge for you, how can you expect to be growing appropriately?

In the last couple days, I've thought a lot about what I cling to for safety. I've tried to challenge myself and see where I can let go.