Financial matters are at the root of much unhappiness. Couples fight about money more than any other issue. People with substantial incomes spend more than they make, yet they still want more stuff. With a few exceptions (like when my employer was 9 months late getting me tuition reimbursement checks I'd been counting on) money isn't an area that causes me great stress.
I chalk most of this up to one thing: I live within my means. With the exception of a house, I don't buy stuff I can't pay for in cash. I do use plastic for convenience, however I pay off my credit card in full every month. Even when I bought my house, I bought a house that I could afford to put 20% down on. I pay a little extra on my mortgage each month so that I can pay off my house as quickly as possible.
I make less than 30k/year. I dated someone once who made 4x that, yet my net worth was greater than his. I could have afforded to lose my job and take some time to find a new one, he could not have.
I am changing jobs soon, and with that will come a nice bump in salary, along with professional status and more vacation days. I don't expect my spending habits to change much. I plan to put a little more into my retirement savings, a bit more into my mortgage, and go to a few more dog shows. That's about it.
I'm not so good at being happy, but I am pretty sure that after one has enough to eat and a comfortable place to sleep, happiness doesn't come from money spent. It comes from living one's life as best one can and filling it with meaningful relationships, paid and unpaid work and experiences.
My advice: Fun doesn't have to cost lots of money. Host a game night with friends - it's virtually free, especially if everyone brings a munchie and/or a favorite game. Plant a garden , or go hiking with the dog. Look at your monthly income and expenditures, and at least force income to be a little bigger than expenditures. Use the excess to pay down debt or build a little cushion. By increasing your financial stability, life will feel a whole lot better.