I'm also really happy and work fewer hours per week than anyone I know.
If there's one thing I worry about it's that I should be trying to be rich because I probably have the means to make that happen. I might be making 200k/yr if I worked full time. I might be able to start a successful company if I put my mind to it. I've never been able to convince myself that it's worth it.
Money just doesn't seem that useful to me. I don't need a car, I'd actually prefer a smaller studio for less money if I could find one. My bills add up to maybe $1400/month. It's trivial to make that much money. I have a fulfilling part time job which I could sleep through and still cover my expenses. Every dollar I earn writing software is a bonus. It constantly surprises me how much money my peers are capable of spending.
Fixing things is also really fun. I have $300 dollar headphones, they cost me $0 because I pulled them out of the trash and spent a couple hours overhauling them. The biggest material source of joy in my life is a $280 bicycle, my laptop cost the same, both off craigslist. Going out for a night on the town can cost hundreds of dollars, if I want to indulge in a vice I can buy enough weed to last me 3 months for the same amount of money. I'm always free to spend time with friends doing cool things.
The skills I have that I use to earn money are all learned from spending free time messing around doing small projects just for the hell of it. I wouldn't have these skills if I didn't have so much free time to explore whatever strikes my fancy.
It really seems like the point at which working harder to earn money hits diminishing returns comes much much earlier that most people think.