That is the secret to happiness as far as I am concerned; measure your days by how much you've learned not by how much you have earned.Yet the vast majority of the time, this sentiment comes from people who are well-off, e.g. someone with an MIT PhD and an almost impossible-to-screw-up future.
There are at least two possibilities. Either people who aren't well-off are just sour grapes, or they deal with a lot more than a lack of proper mindset.
The secret to happiness is no secret: if you have more money than you know what to do with, you can cover the vast majority of cases that will make you unhappy. If you, your children, or your pets get ill, you can get them proper medical care. For someone who lives on $25k/yr, that will almost always end in disaster.
I think it's not productive to pretend like money doesn't equate to happiness. The lust for money can do a lot of damage, but simply realizing that money is incredibly important to happiness is a realization that most people don't make. They spend extravagantly when Christmas comes around; they eat out because they want to "feel like a normal person," i.e. someone who can afford to eat out; they get expensive birthday gifts for family members. And why? Then when a financial disaster comes around, like someone getting ill with no insurance in the US, there are no resources left to deal with it.
I don't know. It's just far too easy to feel like there's a key to happiness waiting to be discovered. It's a multi-faceted and complex issue.