Don't burn yourself out trying to do too much early on in the cruise!
16 nights is a long cruise for someone new to cruising. You will likely have an initial fear of missing out (FOMO), especially over the first few days of the cruise. This can cause you to want be up late into the night and up early the next morning, be sure to pace yourself. You don't want to be 10 days into your cruise wishing it was over because you need a vacation from your vacation.