Cruises have so much going on at any given time, catering to all kinds of individual preferences. If you want your family or group of friends to stick together like glue through the whole vacation, two things will happen: (a) you will miss a lot, and (b) you'll resent each other by the end of it. For example, your husband is fond of the casino, but the last thing you want to do on a warm, tropical day is spend it inside a smoke-filled, noisy room. Go to the pool or spend time lounging on your deck, while he goes to play the slots. You'll both be happy.
This is even more true for couples you might be traveling with. In the case of shore excursions, for example, you all want something different from the island you're visiting. Why not have each couple go off on their own adventure, and then meet for dinner that evening to compare stories.
Traveling with the kids? That's an easy one. They can have fun with their new friends in the kids' club, while you and your honey catch some much-needed alone time. Or one of you go for a relaxing spa treatment while the other climbs a rock wall with Junior.
Vacations are about discovering new people and places, and sometimes that means going it on your own. By enjoying what you like and and then sharing each other's memories, you'll all receive a much more enriching experience.