One bag for a month
Twenty litres, one month, no checked luggage. The first attempt failed politely; the second one worked.
What stayed
Three shirts that dry overnight, one good pair of shoes, a paper notebook, a small first-aid pouch, and a charger that fits every socket I met.
What went home
The second pair of shoes, a heavy book I never opened, and a jacket for weather that never came.
Packing is mostly deciding what you are afraid of. Fear is heavy.