Solo cruise downtime ideas?

I'm taking a 7-day cruise solo and looking for ideas on how to make the most of the downtime.

I'll obviously enjoy the usual cruise stuff (shows, gym, reading, excursions, etc.), but I'd also like to come home feeling like I used the week well.

I'm interested in personal growth, creative projects, learning something new, business ideas, meeting interesting people, or even fun personal challenges.

Any suggestions?