Cruise solo all the time - and not in the retreat. No issues. I do my thing and don't worry about if other people are talking about me. 99% of the time they're too wrapped up in their own vacation.
Read, relax, see shows multiple times if you want. Eat in the dining room and/or specialty restaurants. It's really no big deal.
I love sitting alone - no awkward conversation, and no possibility of having to wait and wait and wait for a table until you find someone who wants to share. Take a book if it's that awkward. I've never had issues with other cruisers (every once in a while they might ask if I'm solo and 9 times out of 10 they are inspired by it), and the servers are always awesome! Best part...you eat at your pace and not that of other people.