Starting a new job at age 40 for the first time since I was 30

I started a new job this week. It's the first time I've started a new job in a decade. A DECADE. Think about how much you change from age 0 to age 10, from age 10 to age 20... Well, I started my last job the year I turned 30, and this is the year I turned 40, and here I am.

Are all 10-year intervals created equal? Is 30-to-40 the same distance as the distance between 5 and 15? 60 and 70?