The search for happiness goes beyond the ages, as is the quest for freedom.
I've found that after working a day job for most of my life, day jobs I never really suck with, that doing what you like is super important. Going out on my own, I did find a new freedom being able to work when I wanted, not to have a boss after me, doing only the work that I liked. But after a while it also became a job. I have to start work at 7:30 every morning (two hours earlier than I did employed) and work until 7:30 at night, I have to answer to sponsors in order to ensure income for the contributors, the developers holding the site together, and myself. All to do what I “liked” but for a while it didn't seem like it was freedom.
Then I realized, that liking what you do, it's not just about doing the “fun” parts. You know, the blogging, the tweeting, the engaging with new and interesting people… it's important to deal with the not fun parts… the figuring out technical problems, accounting, the pressure to be “on” all the time. That every job has it's fun parts and it's boring parts, and no one is immune to that.
What was missing was a sense of gratitude. It's not just enough to like what I do, but to be grateful I get to do it… for a living! Then things started to change, I became happier with my work.
Anyway, this probably has nothing to do with the quote, it's a little off topic… but still, the message is clear, liking what you do (and to be grateful for it) is indeed the path to happiness.