Good point! Many personal financial blogs I read recommend not carrying debit cards in your wallet, but only a certain amount of cash for the week, and when it's gone, it's gone.

I agree about tracking one's money, although writing it down or using a tracking software is just as useful.  I use two (but I like fooling around with budgets and such): You Need a Budget and Quicken. 

I like using my credit card for most purchases for the reason JenniS said - I can look back and see where I spent money in case I forget to record something.

My original post was tongue in cheek to a certain extent - I needed gas in the car and hadn't intended on leaving my wallet at home.