Inadequate emotion regulation may underlie the development of psychopathology as well as worsened physical health, particularly in the context of stress. Cognitive reappraisal is typically considered an adaptive strategy to manage negative emotions. However, the extent to which reappraisal is beneficial may hinge upon contextual and individual differences. Specifically, it is unclear whether and how the ability to reappraise effectively (i.e., reappraisal ability) and exposure to stressful life events moderate the association between habitual reappraisal and health. Using a series of questionnaires and an experimental task designed to measure the ability to effectively down-regulate sad emotions using reappraisal, this dissertation examines the interactive effects of habitual reappraisal, reappraisal ability, and exposure to stressful life events on depressive and anxiety symptoms as well as self-reported physical health. Results indicate that habitual reappraisal may protect against elevated depressive symptoms and worsened self-reported physical health for people exposed to stressful life events, and that reappraising often appears to be particularly important when people are less effective in their attempts. These findings provide novel contributions to the field of emotion regulation and health by clarifying that exposure to stressful life events is an important moderator in the association between reappraisal and health and by elucidating the important roles of both habitual reappraisal and reappraisal ability.