Today is my one-year anniversary, which is a good time to mention another surprising thing I've learned over the past couple of years: happiness isn't fungible.

Fungible means any two are the same, or equivalent. Dollar bills are fungible. I don't care whether you give me one or the other, it's still the same "one dollar".

Whereas a good marriage brings a different flavor of happiness from the kind you get from running a six-minute mile, earning lots of money, seeing a kid smile, or finishing something really hard.

I'm still not convinced the goal of life is to be happy. But to the extent it is, I think it's easy to think getting more of a type of happiness you're good at getting will make up for what you lack. If you have a great marriage but are broke, no amount of marital improvement is going to get you a nicer house. On the other hand, no amount of professional success will make up for poor health, or a lack of love.