Stupidity can be cured, but not as easily as ignorance. No, you aren't really stupid, but we all have stupid habits we should work to replace.
You are ignorant when you don't know something. If you are doing something that is pointless, or worse counterproductive, you can change your behavior and make your life better at a single stroke.
Sometimes, smart people do stupid things even when they know better. The classic example of this is smoking. It costs money, impacts your health, and wastes your time.
Sometimes, they don't do something even if it is in their own self interest. You are guilty of this if you can sign up for a tax deferred savings plan and don't. You are doubly guilty if your employer has even a partial match. They are offering to pay you more without expecting more work. How often does that happen?
Either way, ignorance becomes stupidity when you know the problem but do nothing about it. An ignorant person is either cured or acts stupidly at the moment of revelation. To cure our stupid behaviors -- even smart people have them -- we need to be aware of them.
The first step, realizing your counterproductive behavior, is both easy (recognizing an "aha" moment) and hard (acknowledging it to yourself). The second, stopping that behavior, sounds easier than it may be. It is easy for me, as a non-smoker, to not light up a smoke. For others, the challenge can be immense.
The last step, finding and implementing a productive substitute, may help. Sometimes it is easier to break a bad habit by replacing it with a good one.
For New Year, make a list of things you should stop doing. Pick one and write a plan for eliminating it or replacing it with something positive. Make a resolution and take action to be a little less stupid in 2010.