Why do people compare themselves to others even when they know it makes them unhappy?

Humans are social animals, so the brain naturally checks where we stand relative to other people. This comparison once helped individuals learn about safety, resources, and social rank. Today, it often happens through appearance, achievement, and online visibility. The problem is that comparisons are rarely fair, because people usually present only their best moments. That can make self-evaluation harsher than reality and turn a useful social tool into a source of distress.