Thanks fellow conscious being. I think everyone might experience it in different aspects.

Certainly being an "adult"is one of the greatest reasons for it. Growing up I always thought there was some point in life in which I'd become an adult. After moving out of home, going through uni and now working full time I still don't feel like an "adult".

Maybe that moment comes when you get a mortgage, get married or have kids. But I suspect that no body actually knows what they're doing in this life, some people are just better at pretending.