The negative effects of social media—often called the “dark side”—have become a major topic in both academic research and everyday conversations. Problems like social media fatigue, addiction, sleep disturbances, and compulsive behaviors are growing concerns. One issue that stands out is the Fear of Missing Out (FoMO), which is the anxiety users feel when they believe others are having rewarding experiences without them. Over the past decade, researchers have made progress in understanding what causes FoMO and how it affects people. However, many studies focus mostly on teenagers and young adults, leaving out other groups like working professionals. There’s also still a lot we don’t know about how FoMO impacts mental well-being and daily life. This dissertation explores how FoMO acts as a psychological trigger that leads to other harmful experiences on social media, such as fatigue, obsessive scrolling, and even stalking behavior. It also looks at how these behaviors affect both personal well-being and professional performance. The research is based on five studies: one is a systematic review of 58 past studies, and the other four are new, data-driven studies.