We conducted a longitudinal field study of 13 resource-constrained founder-run textile and apparel firms to understand how and why firms vary in their strategic responses to the same prolonged period of adversity. We discovered that founders use their firms in large part as vehicles to defend who they are or to become who they want to be. Building on social psychological theories of identity, we develop grounded theory and a process model that contribute to the founder identity literature by explaining why and how differences in the structure of founder identity - the set of identities that is enduringly salient to a founder in her/his day-to-day work - drive patterned differences in their firms' strategic responses. Our theory bridges two formerly disparate streams of identity theory and contributes significantly toward theoretical understanding of founder identity by demonstrating how singular or multiple identities and most importantly, the structure of multiple identities, drives the firm's strategic response. The processes we describe help explain responses to adversity but also provide a platform for research that may generate new insights into the significance for founders of bringing "who I am" into closer alignment with "who I want to be."