4. It gets on things. Another sign that you're wearing too much make-up (and too much foundation in particular)? You find a layer of it on the phone after you've been talking only five minutes. You see smears of it on your clothes. And you touch your face and your fingers come away with a thin layer of the stuff. Foundation isn't like pet fur-- it shouldn't be all over everything in your home.
5. You can't feel yourself. When you touch your cheek or your eyelashes, you should be able to feel, well, you. If you run a finger across your lashes and feel only a prickly and inflexible wall of blackness, it should immediately tell you that you've put on too much mascara. Likewise, if you touch your face and feel only the creamy layer of foundation you're wearing, you've put on too much.
It's okay to want to cover what you don't like or accentuate what you do. But if you have to put on layer upon layer of foundation or mascara, it generally means that you need to find a new product. Nothing works miracles, but sometimes better products can make a huge difference in how much you need to wear.