We develop a framework for understanding how social media can reduce both motivation and well-being. Curated social-media feeds raise the bar for feeling successful and distort how people learn about their capability from their own outcomes. Individuals may then work toward an unrealistic standard and misread poor results as evidence of low capability rather than as a consequence of biased comparisons. The result is a motivation trap in which pessimistic beliefs and low effort reinforce one another over time. Social media also reduces well-being by making rewarding moments less frequent. Finally, the model explains why social media can amplify preexisting motivational inequality and why competence-building interventions are especially promising.