I have been through this. It's not as simple as just starting to pay cash, because when you are spending more than you earn, you have gotten yourself accustomed to a higher standard of living; one that is beyond your actual means. Many, many times I would, with the best of intentions, try the cash plan and run out of money within a few days. It's easy to say "well then you're done spending" until you need medicine for your baby or food for your family.
Society has gotten most of us used to a standard of living that is beyond our means. I remember reading a "budget" article that suggested instead of replacing your winter coat EVERY year, to only replace it every TWO years. Sure, that's half, but if you're replacing coats every year in the first place, you're spending a LOT of money, so cutting it in half doesn't necessarily bring it into your actual means.
Another thing that gets me is comparative spending. I'll see something somewhere that's $XX.00, and shop around until I find it at $xx.oo, and feel like I "saved" half. If I didn't need the object in the first place, however, it's still wasted money (or at least money I shouldn't have spent).
Since so many people have just allowed themselves to become accustomed to a higher standard of living through credit, our viewpoints, collectively, of what a "normal" amount of spending for a given income level are skewed. It takes a LOT of really hard work to change your thinking. I still often have to catch myself when I'm going to buy something that I think will make life easier or more convenient, then realize I can either live without it or use something I have (or make something) that will work just as well.
Another BIG hurdle is that, at least in the beginning, you'll be dealing with your new frugality and also dealing with mistakes you've made in the past. For example, if you usually allow yourself $XX.00 for spending, and now want to use that to pay off your credit card, you'll have to actually give up spending for some time. The toughest thing for me was that it wasn't just a switch from spending $500.00 a month on the credit card to spending $500.00 in cash, it was, for several years, a switch to spending $450.00 on the credit card bill and limiting myself to only $50 discretionary spending. That's the hardest part, it really is. The money to pay the bills has to come from SOMEWHERE. (those numbers are just an example to illustrate my point).