One of the traveling light gurus said in a presentation I attended; "Don't pack for the worst case scenario. Pack for the best possible scenario, and then buy things locally during your trip if you run out of something or find you need something else." A decent philosophy IMO. I also remember another snippet of traveling light wisdom that said you should look at every single item you are packing and ask yourself if you will use it enough to justify carrying through your entire trip. Not, "Will I use this?", but rather "Will I use this ENOUGH to justify carrying it in my luggage for the entire trip?" Words to the wise for me.
This last trip, I carried swim goggles and swim fins for use in the pool. I'm not talking scuba diving giant fins, but lap-pool swim-fins. Still, they are bulky for luggage. I used them ONCE in 10 days of travel. The goggles? Yes, they always go with me. They are small and I use them every time I get into a pool. I don't want chlorine in my eyes, and swimming laps, for me, is my preferred cardio when traveling. Less chance of pulling a muscle or straining/spraining something. But fins? I should have left them at home.