There is a difference between carrying something and carrying something. Swinging your 30-pound nephew in the air during a living room play session is much different than lugging him through an amusement park for two hours.
The same is true of hiking. It's one thing to pack your backpack, get it zipped, and strap it on for a test walk around your yard.
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It's entirely different to maneuver across creeks, up steep embankments, and through thick brush with a heavy load pushing and pulling against your intended movements.
Cut weight everywhere you can. Find lighter materials for the pack itself, as well as for everything you put in it. Carefully balance the bag to keep the weight low and close to your body. And strap it securely and tightly to your body, so that it's an extension of you instead of a separate item with a mind of its own.
That's a look at weight, but let's remember bulk as well. Even though items may be fairly light, their bulk can cause problems. Smaller items that are far from your body's center of gravity will utilize leverage to increase fatigue. They will affect your posture, which in time will cause pain and slow your progress.
Bulk creates decision-making issues as well. You want the most value per unit of volume in your backpack. Tiny energy bars are dense and helpful. Huge sloshing bottles of plain water are not. Augment the utility of your hydration by including a tiny packet of sports drink powder that will add electrolytes and energy with your hydration.
And think about your ability to fit into spaces. If you encounter areas where crawling is required, you may struggle to fit through narrow passages if you're carrying a massive backpack full of fluff you don't need. This can also slow your movement if you should suddenly have to flee danger such as an animal or dangerous weather.
Nothing is more important in your excursion as the planning process. If you spend some quality time thinking about what you really need to take and what you really don't need, your trip will be more successful and more memorable.