I am the queen of over packing (well, Disney Mom Tanya might be the queen, but I definitely qualify as a princess!), but I have found the key to helping me stay organized and to keep me from packing things we will never need at Walt Disney World (I actually packed mittens one year to take the girls through the former Ice Station Cool!). When I get ready to go now, I print out a comprehensive list of things you might possibly need, and I simply go down the list, cross off things I know I won't need, and check mark the other things as I pack them.
The most comprehensive list I have found is at
www.themouseforless.com . If you go to their website, and at the bottom on the left in the search box type "packing list", the first entry that pops up is the list. You just have to click how you want to open it (.pdf, Word document, etc.). The list is broken down by what you might need in your suitcase, what you might want in your backpack for the theme parks, what you could take into the water parks with you, and even a list of things you would include if you were staying at a villa with a kitchen.
They also give a check list of things to do before you leave - like stop your mail, alert a neighbor, etc. It's a great tool when getting ready for any vacation.
Have a great trip!