Realizing the power of midtones and darks, as opposed to highlights, has improved my drawing. Every area must have a tone, even in the light most facing plane. I used to think that paintings were made with strong highlights, but that is not true at all.
A darker, more accurately toned, drawing will always look more appealing than a blown out highlight drawing. And this is true because life has very few lights. Skin and a lot of other materials are mostly softly shifting midtones. But, as always, it's important to balance all the factors.