Overpacking usually comes from thinking in items instead of outfits. You throw in extra tops just in case, and end up carrying clothes you never wear. Packing light is really about choosing pieces that combine.
Pack a mini capsule
Choose pieces in one colour family so everything pairs. A few tops, two bottoms, one layer, and versatile shoes can produce a week of different looks when they all match each other.
Plan outfits, then pack them
Decide the actual looks you will wear before you pack, and only bring what those outfits need. If a piece does not fit into at least two outfits, leave it home.
Let an app do the combinations
Working out mix-and-match looks by hand is fiddly. Lookify composes outfits from the clothes you choose, so you can see how far a small set stretches before you zip the bag. Wardrobe-Only mode keeps it all to pieces you own.