When I'm counseling people with money trouble I make them do this. It's cash for EVERYTHING where possible. (and I'm not suggesting you have money problems). But if some one wants to really get a handle on their finances... a written, posted budget and a cash only system is a GREAT way to start. The whole rewards card thing is great and all - but requires discipline.
Did you know that many credit cards will let you set up self-imposed spending limits? I think it's smart to have people live on a budget via cash, but it can be dangerous as well. My parents live almost exclusively on cash/debit. They destroyed their credit early in life. I grew up seeing what a boom/bust house looks like. Every two weeks our cupbards were full, then they weren't, then they were, then they weren't. Money management is SO important. Thankfully, I married the woman I did. She really changed me. For the better. We live within our means and it's a good feeling. But you're right, it requires discipline.
It's interesting you say that. The whole reason I switched to cash actually was because all the time now you hear about stolen credit card data. If I pay in cash, that's one less thing I have to worry about. I just discovered by accident that it allows me to control my spending habits better. It's so helpful that it actually overshadows my desire to keep my credit card data safe as a motivator to use cash. Now it's something I recommend to anyone to try out if I hear they're having problems with budget.