Overpacking is the most common first-trip tax. Underpacking creates expensive replacements. Aim for a kit you can rebuild in any mid-size city.
Specialty gadgets you have not used in 30 days, duplicate toiletries, and “just in case” clothes for imaginary events. If an item is cheap and available at destination, buy it there.
Revisit your bag after every trip. The best packing list is the one your past self already stress-tested.