Your immunity. "mucor" is an invasive fungus that affects people with severe underlying illness like very poorly controlled diabetes, or immune suppression for transplants, and autoimmune diseases. Some malignancies (leukemias) can render your immune system ineffective. If you don't have these conditions or similarly severe illness, you'd be hard pressed to get mucormycosis even if you tried.
Mucormycosis. The group of molds that cause mucormycosis, also called xygomycosis, are quite common in the environment. Avoiding the spores of these molds is basically impossible. Since the classical patient with mucormycosis is the uncontrolled diabetic, keeping diabetes controlled is an important way of avoiding the infection.