I'm not sure happiness is the thing to think about. It's meaning that's important. Happiness is a sort of evolutionary trickery to help your savannah-dwelling ancestors. Meaning is something they'd have almost no perspective on, given what's happened in between.
For me I've gotten to this stage where I feel like it's a long way between things that are entirely new.
Personally I've seen deaths, illnesses, births, weddings, divorces. Lots of all of them, from near and far.
Professionally, I've been a junior guy and a senior guy. A founder, individual contributor, a leader, a follower. Seen businesses go well, and go under. Been hired and fired, hired and fired others.
In terms of observations about the world, I'm by no means an expert on everything, but whenever something comes up I can more or less place it. I know roughly what X is, and how other people see it. I no longer get that "holy crap, I never knew tax optimization employed so many people". Or "that declarative languages stuff, it's more important than I first realized".
Same with social, economic, and political stuff. I'm not surprised to run into one or another observance anymore. And I've heard the arguments before. Sometimes better made, but the same stuff.
Science and math seem to still have that potential, so I'm gonna mine that. Things like NNs still throw up new things, even if they can be glued to a long history of thought. And observations about physics can still fascinate, though in little pieces.
I'm thinking cybersecurity next as somewhere to dig as well.