It can be difficult to get yourself in the mood but if you can then I find that exercise can be really helpful. I know this is a challenge if you are in quarantine but there are lots of exercise videos you can try :)
One of the best things, I find, is having a good old laugh, perhaps with a partner, roommate, close friend, or family member. Stand-up comedy/cat videos/films can also come in handy.
If you like to read, then books can be a great escape. If I'm feeling down then I'll look for something absorbing and not too cerebral. If you like magic or fantasy, I really recommend Jonathan Strange & Mr Norrell, and for something historical, you might enjoy Wolf Hall. They're both quite long but in a good way.
If you're after something a little more "deep", then poetry can be really comforting. Some of favourites are Emily Dickinson, Philip Larkin, Audre Lorde, Walt Whitman, Charles Baudelaire, Sylvia Plath, and Federico Garcia Lorca.
I hope you feel better soon.