Yes the whole "You get used to it" rationale is utter nonsense.

I was born and raised in Denmark, but lived in Texas for 20+ years and I never got used to the heat... in fact, I rarely ventured outside between May and mid-September. Now I live in western Washington state which is cool/temperate much like Denmark, and I feel "home" here.

South-East Asia just doesn't have my type of climate. I expect the only climate in Vietnam I might be able to tolerate would be Dalat, which I hear can be pretty nice since it's a mile high.