toughen

This term describes a transition toward greater durability, whether in a physical material or a human psyche. When applied to materials, it suggests a technical process of increasing resistance to fracture or wear, often implying a chemical or structural change. When applied to people, it carries a connotation of hardening through adversity. It suggests that the subject has developed a protective emotional shell or a more disciplined will as a direct result of hardship, stress, or rigorous training.