Packing light is a skill that gets easier with practice, but most travelers overpack out of habit rather than necessity. A carry-on that fits everything you actually need makes a trip smoother from the first step out the door to the moment you're waiting at baggage claim - or better yet, walking straight past it.
Most travelers wear a fraction of what they pack. Laying out everything you plan to bring and removing anything you can't picture using more than once is one of the simplest ways to trim a bag down. Laundry, even hand-washed in a sink, also does more work than most people give it credit for on trips longer than a few days.
A useful test is to ask whether an item solves a real, specific need for this particular trip, rather than a hypothetical one. Packing "just in case" items is one of the most common ways a light bag turns into a heavy one, and most of those items end up coming home untouched.
Packing well isn't about bringing less for its own sake - it's about bringing exactly what a trip calls for, nothing more. Once that habit sets in, a carry-on stops feeling like a constraint and starts feeling like the easier way to travel.