This trial is part of a multi-phase study to develop and test positive psychology (PP) interventions in patients hospitalized for an acute coronary syndrome (ACS).Using a factorial design, the investigators will: (a) assess the optimal frequency of exercise completion, (b) determine the utility of 'booster sessions' after an initial 8-week intervention, and (c) determine the relative merits of utilizing PP exercises alone versus an intervention combining PP with motivational interviewing (MI).