To start you off:
There's tons of other options as well.
- Go out for a run/walk, enjoy nature.
- Go to the library and read a book.
- Study something new, learn a new skill.
- Take up a new hobby.
- Catch up on a series you've been meaning to watch.
- Attend a social event. Meet new people.
- If you have the money and time, go travel. Doesn't have to be far.
- Learn to play an instrument.
There's tons of other options as well.