FOMO is "Fear of Missing Out" (which means it should probably be 'FoMo,' because the prepositions don't need to be capitalized). Its definition is:
"anxiety that an exciting or interesting event may currently be happening elsewhere, often aroused by posts seen on a social media website."It's evidently a phenomenon for today's young people.
I am raising a teenager, and I am glad that he doesn't have FOMO at all. He has FoNBAtPLoL, also known as "Fear of Not Being Allowed to Play League of Legends." From the perspective of a parent or guardian, this is not a bad thing at all. Homework? Chores? Behavior at school? FoNBAtPLoL keeps it all sorted.