What causes people to stay in relationships that make them unhappy?

Several psychological and practical factors keep people in unhappy relationships. Emotionally, people experience what researchers call the "sunk cost fallacy," where they feel too invested in time, energy, and shared history to leave. Fear plays a major role too, including fear of loneliness, fear of the unknown, or fear of a partner's reaction. Low self-esteem can make people feel they don't deserve better or couldn't find someone else. Practical barriers matter as well, such as shared finances, children, housing, or social networks built around the couple. In some cases, cycles of intermittent reinforcement, where good moments follow bad ones unpredictably, create strong emotional bonds similar to those seen in addiction. Social and family pressure to stay together also reinforces remaining in unhealthy situations.