I am one who travels with an 18 inch carry-on for up to 2 weeks. For me, the key is color coding the wardrobe. I have black pants and skirts that pair with every top I pack. A real cliche, but scarves do dress up an outfit and take little room. I generally manage with 2 pairs of shoes - the heaviest walking shoes are worn and a dressier shoe in the carry-on. For 6 nights, I would pack one skirt, 2 pairs of pants and 3 tops - knit and pullover sweater for that time of year. I pack a silk camisole for under the shirts and find that works the same as layering with more bulky sweaters or jackets. On the plane, I have my coat, usually an all-weather coat with removable lining, gloves and the most comfortable travel pants I own. Sleep/loungewear includes light ballet type slippers (I can’t wear flip flops which would also work for hotel) and lightweight nightgown that doesn’t require a robe to be “decent”. I swim and fit a suit in depending on the hotel. On a longer stay, I do rinse out underwear and have also done that with a knit top.
Several times, I’ve had my carry-on suitcase weighed, so I do monitor how much I put in. It’s really the books and documents that I’m sometimes carrying that add the weight, not clothes! I also have several Travelon and Pacsafe purses that easily fit Iphone, mini Ipad, wallet, guidebook, cosmetics/toiletries in the airline required quart bag, etc. It helps me to think of the purse as part of the overall packing scheme.
On a recent trip, I had to check a bag because of some heavy documents that needed to be delivered on arrival. I used the opportunity to pack more clothes than I normaly would - and didn’t need a lot of what I packed! Once you get organized, it is really a sense of freedom to travel lightly!
Have fun!!