In other times of my life, I have quit my job and spent half a year writing free software, or training karate -- without any income. I also spent 5 years living in a run down shack spending less than $10K a year, when I was teaching English in Japan.
By many measures, I was living in poverty because I had almost no income, or I was spending almost no money. But at no time in my life have I ever thought of myself as poor. I have always had money in the bank and I have never really been in debt. When I went hungry it was because I stupidly spent my food budget on beer (or something similar). I didn't have money for food, but I did have money.
Money is an option to buy things and for me the feeling of being rich is the feeling of always having that option. You can be happy with less things, I think. Nobody actually needs a yacht to be happy, or a big house, or a collection of vintage wine. But I think it is really hard to be happy when you have no options. It is even harder to be happy when you spend your options in the future and have to suffer with crushing debt -- possibly enslaved forever.
I could choose to be hungry. I could choose to give up my job and do something that paid no money. I could choose to move half way around the world and live in a shack teaching English. That's incredible wealth for me. That kind of wealth is available to many people, but I think that most people can't see it, unfortunately.