Fitting room mirrors are a very curious thing. For one thing, they're designed to make you look so sick and so horrible that you decide that the only thing that could make you look halfway decent would be to get a brand new, stylish wardrobe and then a makeover in the makeup department. However, clothes that will not look good at home look quite nice in the fitting room. Shirts stay right where they should so that your bra straps and cleavage don't start hanging out until you get home. Elastic waist pants can actually lay flat and not make it look like you keep an inner tube around your waist. Thin skirts look so great that you don't realize the length of your steps will be cut in half when you wear them.
It's really an evil plot designed to separate you from your money and make you feel so low that you'll treat yourself to makeup, jewelry, and new shoes.