One way to become a better packer is to make a list of everything you brought last time. Cross off all the things you didn't use on your trip, or at least could have gotten by without using. Take a look at the remaining list with a very critical eye, and try to narrow it down further.
As for toiletries, I don't ever take full sizes of anything. I take whatever's available in a travel size, and I try to consolidate where possible. For instance, i don't pack a face sunscreen and moisturizer and foundation - I use a BB cream when traveling. That's one small tube. I don't use my regular shampoo and conditioner, I take individual packets of Wen, or something from the drugstore in a travel size. It won't ruin my hair to use something different for a few days. Travel size deodorant from the drug store. I use whatever soap or body wash they have at the resort. I buy sunscreen at the resort. I take as few cosmetics as possible, in as small a size as possible. I just pick neutral shades of eyeshadow and lipstick that go with anything. If it doesn't fit in a small cosmetic bag, it doesn't go.