I have forgotten how to live

The previous years of my life feels like a dream. I was happily living, consumed with studies, learning things, watching youtube and stuff, enjoying a lot, mind was busy in various entertaining stuffs. But, I don't know how it started, but all those passions are waning. Its almost as if I've forgotten how to live. Live as in the previous ways of my living. I am now trying to find a way to live as I've lived in the past but can't seem to go back to the old ways. I mean I want to find something fun for my mind as I had in the past but I just cant bring up enough passion. What is happening to me ?