In times of sickness, we tend to look poorly at our circumstances. "Life isn't fair." Life is only a projection of the energy you poor into the universe and yourself. If you use Black Tourmaline to block out these feelings, yet continue to do them, is it the crystal's fault?
Crystals are tools for us to enhance our earthly experience, not a replacement for self responsibility. They can show us deeper versions of ourselves, but only if we let them. A giant piece of Selenite may be beautiful and have tons of natural power, but like all things, only power we give it.