I live alone and I’m not in a bubble with anyone so even though I have lots of people living close to me, it’s like being on a desert island most of the time.
A few tips: make lists, tick things off as you compete them from the list, sort out music playlists, exercise, stretch, watch some box sets, watch some films, cook well...eat well, write some memorable stories from your life down, look at old photos, read (I don’t ever really read personally, I’ve never read a book from the first word to the last ever! but some people love it), draw, keep the house/flat clean...
Basically keep yourself as busy as you can and you even strive for times of the day where you’re just sat there with your eyes shut having a res. The busier you are, you don’t even notice that you’re alone!