Packing

This is always a dilemna, I hold two opposing views on packing simultaneously.
Do I take everything I could possibly need so I can say "a left handed nurgle sproket adjuster, I have one here!" and kill myself with the sheer weight of equipment or do I follow the other philosophy, a small empty bag and a credit card? This has the problem that although the regions I'm travelling in are undeniably civilised they are also foreign and therefore inclined to not having the most simple and usual products that home supplies. A head cold in London sent me out for vitamen c tablets, preferably combined with garlic and if I was very lucky, horseraddish, This straightforward purchase was totally stymied by the English habit of putting cod-liver oil in everything and not being into garlic at all. Foreigners are very odd, thats what you go for but there are times when you wonder how they can possibly flourish so lacking are they in life's basic ammenities.
My usual compromise is to buy/acquire everything I think is necessary, pack it, try and lift it, then leave most of it behind. Not perhaps the most efficient process but it does allow you to think when that nurgle sproket needs adjusting that you had at least forseen that this might be a problem and had it not been for weight restrictions you would have been totally prepared.