Personally, I do my best to only spend money I have. I avoid debt. I just recently paid off some student loans and became 100% debt-free.
I don't use credit cards, except for online purchases, which I pay off immediately. This is just general personal finance common sense. I know I can always make more money if I wanted to buy something I couldn't afford yet, but I'm a minimalist anyway, so I don't tend to buy a lot of material possessions. I'm very happy with what I have.
Edit: Sorry, this wasn't really a "LoA" type of response, if that's what you were looking for.