I know that lots of people keep a $100 or $500 or even $1000 buffer in their checking account which they are not "allowed" to spend, but I think I am just congenitally unable to do that. I switched from using credit exclusively to using a debit card exclusively about six months ago (which was temporarily painful on the budget) but I am doing OK with it now. I switched mainly because I was spending too much money each month because I have a higher credit limit than I have money to spend - an old tale to be sure.
So now, if I have extra money that I need to save (for example, $900 that I have put aside for next month when Boyfriend will not get paid anything) it has to come OUT of the checking account. (It is in my linked savings account right now.) I need to remove the money from the account - so that anything in there is for Spending Only.
I'm not sure why I can never keep that buffer in my account. I'd certainly like to - I sometimes get down pretty close and have worried that I would overdraw. I think what is going on is that I suffer from "I'll put it back" syndrome - where things that seem like a necessity right now will start to spring leaks in my buffer, and pretty soon there will be no buffer at all. It's kind of like the big problem with payday loans - you need one because there was an unforeseen emergency, but you don't have the money next month to pay off the loan because your pay doesn't usually vary that much, so if you made enough to easily repay the loan, you would make enough to easily cover the emergency in the first place! I know that when I take money out of the buffer that it needs to go back next month - but then my spending is curtailed next month, and I see that buffer, and I think, well I'll put it back next month...
Thus, no buffer. And no credit cards. Keeps me legal.