They say to never shop for groceries when you're hungry, and the same rule holds true for Pisces and shopping for beauty/fashion loot.
You can be a moody soul and, unless you have a bottomless bank account, should stay away from the mall or even popular online sites when you're feeling down. You can also be hard on yourself, and play the martyr game.
Going shopping with a trusted friend can make the difference between feeling confident and stylish, and being so hard on yourself that you go home crying or broke. Remember that beauty is found in all shapes and sizes, and it's not what's on the surface that matters.