this happened to my family as well. The amount of money you can save by being frugal is very limited. IMO you're better off living a reasonable lifestyle and focus on income rather than expenditures.
The point is find eliminate spending on stuff that doesn't really make you happier, and focus on the things that do. Also, find cheap hobbies, reading, etc. etc.
for software guys like mmm I'd wager that it's better to take the time and energy used on frugality and instead try to develop alternative income streams, which ironically is exactly what mmm did.
regrets over $10-30 purchases seem like a complete waste of time to me... https://www.newyorker.com/magazine/2016/02/29/mr-money-musta...