It doesn't work so well for money because there're at least some external constraints on wealth, but for happiness, it really is purely mental and your "guide" will work perfectly well for most people. Well, the ones who're willing to take enough of a leap to follow it.

Apparently some people need to be reminded!

Some of the best advice I was ever given was that if you want to be rich, live like you're poor. Most people, left unchecked, will live to the extent of their means, which is a tremendous contributor to debt, because a) when you want something above what you already tend to buy, you do it on credit, and b) credit is carefully constructed to take forever to pay off if you are only paying what you have to.

So, the advice could better be stated "spend less, put what you don't spend towards eliminating your debt".