Will cancelling a credit card hurt my credit score?

I'm 21 years old with a credit of about 669. I've paid off one loan completely, and just purchased a new car (100% bank financed), the only other bills I have are a cell phone and of course insurance for my car, and a small life insurance plan. I have one credit card with a max limit of $1900 that I've had for about 3 or 4 years now. My balance is almost paid off and I'm trying to decide whether or not to close the account. I've had a lot of trouble out of the company and having that $1900 staring me in the face all the time is very tempting to spend. I've recently cut the card and trashed it so I couldn't spend anything but the card did come in handy a few times when I was strapped for cash and needed some in an emergency. Someone told me cancelling it will lower my credit score. True? I thought about cancelling this one since the company is lame and trying to find another one to keep for emergencies but I'm not sure. Any advice is greatly appreciated!