I was in a similar situation 10 years ago
I used to go theater to watch movies alone
Used to learn and teach juniors online, earning extra income, and used to enjoy investing some portion
Also used to go iskon to understand scientific Geeta courses and got few people to interact with
Also used to visit hometown regular basis without thinking about travel fare amount
We should invest money on ourselves, it could be anything which makes you happy like learning, shopping eating out, giving gifts, etc
All the best