I have overpacked for every trip I took in my twenties. The list below is what is left after ten years of carrying things I never used.
Three shirts, two trousers, one warm layer, one waterproof. A paperback I have already started. One camera, one lens, two spare batteries. A notebook with a pencil tucked into the spine.
What I leave behind
The second lens. The laptop. The tripod I always think I will need and never set up. The just-in-case clothes for an occasion that does not exist.
A lighter bag makes a different kind of trip. You walk further, you say yes to the bus, and you stop treating your luggage as a second job.