use credit carefully, if at all

My parents taught me never to buy anything on credit that I didn't have the money for right then.  They used credit cards mostly as a convenience so they wouldn't have to carry a lot of cash with them.  I am disciplined enough that I don't spend more when using a credit card than I would if using cash or a debit card.  I was able to accumulate several hundred dollars on my Citibank Driver's Edge card years ago mostly by purchasing groceries.  The money had to be used toward the purchase of a new or used car. But if I had seen that I was spending more money because of the card, I wouldn't have used it.  For many people, its too easy to forget to keep track of their spending and be surpised by the size of their credit card bill.  Sometimes they can't pay it off and have to pay large amounts of interest.  This quickly adds up.  Do you want to pay a bank hundreds of dollars of your hard earned money because you couldn't wait to buy something until you had saved enough money to pay for it?