Sure, although the age of credit accounts is a significant factor in your credit score, so it's not advisable if you are trying to build credit.

Personally I have enough practice that I treat my credit cards no different than I would treat my checkbook—it's not that hard to avoid trouble if you just have the mentality of only spending money you already have. In other words, I personally don't think cancelling the credit card is necessary, but YMMV.