A friend asked what we did in the evenings in France. My answer? We went to sleep. Usually by 9:30 pm or so.
Maybe that’s partly because of the time difference. France is 6 hours ahead. But we were there for about 10 days, which is a pretty good amount of time to adjust.
I think we were exhausted because being in a foreign environment makes your brain work overtime, even to do mundane things that you take for granted in your usual habitat.
Simply going to the bakery or grocery store and buying a few items is a big deal if you speak only a few words of the language. Road signs are different. The car dashboard (in this case a rented Renault) is different. Waiters and shopkeepers may or may not make any allowance for the fact that you are obviously straining to follow their questions.
It keeps your mind working overtime, like running a mental marathon.
Not quite as extreme as this neurobic exercise, but still pretty darn good.