Trust in others is essential for the well-functioning of societies. While economists often study its longer-term determinants, short-term fluctuation may be equally critical, particularly during pivotal moments (e.g, elections) or periods requiring social cohesion (e.g., pandemics). Hope plays a similarly vital role in shaping individual well-being, behavior, and societal stability. We investigate the short-run plasticity of trust and hope by reactivating threat exposure similar to that encountered in media coverage. In an online experiment, individuals are randomly exposed to short videos depicting terrorism, natural disasters, or war. Both social trust and hope are significantly malleable, declining by 12%-28% of a standard deviation (across models) in response to these brief interventions. We observe strong heterogeneity in these effects, particularly along lines of political orientation and social media usage, and explore their co-movements with basic emotions. Our findings suggest that routine exposure to threatening content can destabilize the emotional underpinnings of trust and hope, with potential implications for key individual and collective behaviors.