Yesterday I came across a posting on a blog called Dual Income No Kids, which offered an interesting alternative to cutting up your cards to control spending.
If you really think you need to keep that card for emergencies, then try freezing it. When I say freeze it I mean fill a mug with water and put it in your freezer. This way if you want to use your card, you are going to have to wait for it to thaw out. As it thaws, so too may your urge to buy whatever it is you think you need. I might try this idea.