“ I always take too much “ , “ where’s my &$#@“ now I have to buy one!
The lament of packing.I’ve experienced myself.
Over the years of travelling both for work & adventure I have learnt a few lessons for what to take & take out of your bag but believe me I’m not perfect.
Depending on your trip= different items ( of course I know your saying ) however here are things I always pack.
Swimwear. you never know where a pool or spa in snow or lake while hiking the Milford Track .Thongs, flip flops jandles whatever you call them pack a pair, Comfy walking shoes .Scarf that can be used as a wrap, sarong or dressing up a outfit. A pair of decent leggings that can be used for a day of walking or wear with oversized top to have a outfit or if the weather turns icy under pants for extra warmth.
Ear plugs for flights, noisy hotel rooms, or just to block out your companion.

Woollen wrap even in tropical climates the nights can be cool, also great on transport, over your bed too.

Even when travelling I like a few nice products.
I absolutely LOVE Lush products they make some beautiful shampoo & conditioner bars, easy to pack & no spillage. Sunscreen.

My other essential is a Swiss Army Knife( packed in your hold luggage if flying) & good bottle opener. Cheese & Wine anyone !!!