Check your Defrost and Heater units.
When our windshields fog up in the winter, it's because moisture from inside the car condenses on the glass and makes it very difficult to see. Water vapor coming in from an open window or even your own breathing can fog up a window. Defrosters solve this problem by blowing warm, dry air over the glass by also engaging the A/C system. If you're sure your defroster unit is functioning properly but there's still a problem with too much fogging, bring your car in to get checked for proper A/c system function and also check for air leaks around doors and windows that could be letting extra moisture in.
Remember, it's also important to stay warm and comfortable while driving, since shivering makes it difficult to steer or pay attention to the road. If your heater isn't working, you may have a faulty or plugged up heater core. Although heater cores are expensive to replace, it will be worth it during the cold winter mornings if you don't want to freeze behind the wheel. Give us a call if you are experiencing any defrost or heater issues.