How to pack for a cruise? (Teach me!!)

I have no clue how to pack or what to bring. I'm going on a 7 day Caribbean cruise and from what the dress code rules say I need to change like 3 times a day! I over pack as it is and it's really stressing me out. What in the heck do I do here? Tell me what you brought on your cruse and what is a must to bring. Also tell me some stuff you brought that now you wish you would have left at home.