Psoriasis Pustulosa Palmoplantaris

A 52-year-old woman presents with a 3-year history of painful crops of deep yellow pustules confined to her palms and soles, with background erythema and scaling. She reports a 30-year smoking history. Cultures of the pustular fluid are sterile. The condition shown as **C** in the diagram is suspected. Which of the following is the MOST important non-pharmacologic intervention to reduce disease activity and prevent relapse?