I agree with Doug. Relax and have fun on your cruise! You are far safer on a ship than you are wandering the streets of any big city.
For some reason, cruise ships fascinate the general public. And consequently fascinate the news media. Therefore, anytime something unusual happens on a ship (norovirus, accidents, etc) it makes the news -- but when norovirus shuts down the local kiddie daycare, or somebody gets hit by a truck, it doesn't make the news.
It's the same phenomenon that happens with airline accidents. Far more people are killed in auto accidents -- but it's the airline ones that make the news.
So have fun on your cruise! Eat, drink, and be merry! You'll be safe, and you'll have a great time -- I promise!