Resilience in illness is often treated as a stable personal resource, yet illness journeys alter physiological burden, emotional demands, coping options, relationships, and opportunities to participate in care. This article develops a proposed biopsychosocial theory in which patient resilience is a time-varying capacity to preserve or reorganize adaptive functioning under illness-related demand. Biological burden constrains feasible adaptation; appraisal and emotional regulation shape interpretation; coping flexibility supports context-sensitive action; relational resources determine whether support is usable; and healthcare participation becomes adaptive when patients can convert knowledge, preferences, and effort into consequential involvement. Resilience can also be depleted when demands accumulate, support is mismatched, participation is obstructed, or self-management work exceeds available resources. The theory therefore shifts attention from identifying “resilient patients” toward explaining changing demand-resource configurations across illness transitions, while separating resilience from distress absence, adherence, activation, any single coping strategy, and clinical outcome.
