I startedd to feel something like that too, basically a few weeks from the quarantine. The thing is, I actually thought I would like being closed up, because I'm pretty introverted and don't mind staying at home after work. However, the last couple of years I've started going out more, meeting new people, and trying various activities, which really opened up my view and felt good. But I didn't imagine that cutting these things off would affect me that much. Now I don't even want to work, don't want to play games either, can hardly force myself to watch a movie too. That subtle "background sadness" is a pretty accurate description.
