People who have a hard time exercising willpower over their credit card use sometimes find it necessary/helpful to take some extreme steps. Besides cutting them up or freezing them, Lifehacker points out that serial impulse-swipers can help limit their spending by demagnetizing their cards. Just rub a high-strength magnet, like the kind found in a hard-drive, over the strip. It will be harder to go for a spree at the mall because the card number would have to be punched in by hand, but you will be able to make purchases online for airline tickets and such. If the primary way that you overspend is through a real-world shopping romp, this could be one way to curb your bad habit.