I tend to take way too much on trips. But, the last couple of times, I've done better. As Oak stated, most of my trouble comes from the varying types of exercise apparel and shoes I bring. When we have gone to Europe on cycling tours that included 2-3 days of city relaxing on both ends (2 weeks or so total), we each bring one huge suitcase that is legal size. Then we have one duffel type bag that is for helmets, shoes, saddles, and pedals that we brought for the rental bikes. And, I have a large "purse" type leather bag I use as a carry on. The airlines we use to fly to Europe don't charge for baggage.
However, the last 2 times I went to Phoenix for my in-laws memorial services, we did long weekends (4 days) where I put everything in a carry on. The last time included hiking shoes and clothes for 3 days of hiking. That was a miracle.