The concept of investment bias, also known as sunk cost fallacy, plays a significant role in why people stay in bad relationships. This bias refers to the tendency to continue investing time, effort, and resources into something, even when it is clear that those investments are not yielding positive returns. People often believe that because they have already invested so much in their current relationship, it makes sense to continue trying to make it work, even if the relationship is fundamentally flawed. The fear of change can paralyze someone in a bad relationship as they prefer the perceived stability of an unhappy partnership over the uncertainty of a future on their own.