Many women end up looking they have a floating head or they are wearing a mask because their foundation does not match their face and neck. When you go too light it makes your skin appear flat and lifeless. Instead of natural, it will look like the makeup is just sitting on your skin, which can add years to your face.
But if you go too dark, you are not highlighting your features, but dragging them down and adding a dullness and heaviness that is just as aging.
In order to get the right color, when testing out a foundation, do not blend it in too much. Simply tap it on your face from the top of your cheekbone to the bottom of your jawline and try to not go lighter or darker than your actual skin.