A subject close to my heart, and which while certainly helpful is philosophically unrelated to financial well-being, is minimalism.
A word of honesty before we begin: I am not a good minimalist.
There are many reasons for this, but the primary one is that the people I share my life with are not minimalists. This is not a judgement, they’re very happy the way they are! As a consequence, there’s a lot of backsliding in my path to minimalism.
That said, there’s a lot in common with the philosophy of minimalism and the philosophy of living well within your means.