A comprehensive file with firstly a printed list to work though at home - car fuel/oil level/tyre pressures/stop cock / house heating settings /spare key /tell trusty friend or neighbour etc. You feel calm and in control once you have worked through it.
A second file list with packing notes for the specific type of destination (UK/overseas sporty/or sightseeing)
Packing cubes - with a list against the physical activities you will be doing / yoga/sailing/city walking/or dressy
Crocs - ugly (maybe) but lightweight and can cover so many activities - in the shower/washrooms/poolside/beach walking/city walking/over rocks and to go in the sea in any terrain.
microfibre beach towels/sarong - Decathlon do bathsheet size, lightweight, compact, brilliant
Rucksack and beach bags - pre packed at home with all contents you need - to just unpack at destination and literally go
Turkish towel, multi functional.
Cosmetics in a cheap ASDA sandwich box - literally unpack and place in bathroom
Another similarplastic box for bedside essentials (tablets/alarm clock/nailfiles/pen)
Finally, for the adventurous, a polyester print sarong so you can sea swim at a moments notice literally anywhere that takes your fancy….no swimsuit, no knicks, literally just the sarong. …..and literally no one ever notices.
(……alas not for doing tumble-turns in the pool though)