Pack half of what you think you'll need, bring plenty of sunscreen, make sure you have your sunglasses. Read your newsletter daily and go to activities that interest you. They have activities for singles, if interested attend them, it's a good way to meet people. You can pre-book your excursions, however, you may meet some people on board that enjoy doing what you enjoy and want to book excursions with them. You can book on board, either at the excursion office or on your tv in your room. I've done a few cruises solo and had a wonderful time. It's great to go where you want, when you want and not have to worry about anyone nagging you.
On one of my solo cruises I brought a couple of books that I thought I'd have time to read, however, I didn't get through the first chapter until I was on the plane going home. You will meet some really great people on board and have a wonderful time. My one suggestion is to stay with a group while touring any port. I ventured out once on my own in Jamaica and quickly realized that wasn't a good idea. No harm, no foul, but I should have not done that. We were in town for a shopping stop and I smelled Jerk cooking, so I wandered away from the rest of the crowd. I quickly came to my senses (after purchasing the best jerk chicken I've ever had) and rejoined a pack of fellow cruises. Relax and have the time of your life! Best wishes!