First, sometimes you have inappropriate clothing. It is hard to anticipate every need. We try to strike a balance between cold and warm weather clothes. I myself can layer. For example, on our trip to Germany, we had rain 35 out of 37 days, and I sure would have liked another pair of jeans and less shorts. But I made due with what I had and was OK (though at times I had to dry stuff out in the room overnight). This past summer I cursed my worthless, heavy, space-wasting pair of jeans and fleece... until we hit cooler weather in the north. Still, for six weeks I was kicking myself.
This happened to Gail on this past trip, when she was cold because she packed summer beach wear. We had no idea (from weather.com) that it would end up being cold, windy and rainy.
The solution: It is called money. We bought her some additional clothes.
Second, I really miss my multi-tool, and we cannot carry a corkscrew. The first trip we were a little bothered that we only had small deodorant, toothpaste and so on due to the TSA rules.
The solution: Actually, this has turned out to be one of those pleasant surprises in travel.
We have learned new words (cavatoppo is corkscrew in Italian) and had fun meeting people, who are surprisingly willing to lend us a korkenzieher (German)... sometimes inviting themselves to a drink with us! Once, I needed a couteau (French for knife) and I not only learned the word, but bought a really nice Opinel knife, cheap, AND I got to keep it because I learned how to mail it home, therefore bypassing all these silly carry-on regulations!
In addition, there are these things around the world called stores, and other things called ATMs. It is amazing that the United States is NOT the only place to buy toothpaste! And the French brands are surprisingly good.