Equilibrium
We very quickly get used any changes in environment and they become the norm.
Today it’s 28° and I’m actually cold walking around, because for the last week it’s been 38°+. In the UK, 28° is about as hot as it gets on a normal summer day.
Similarly, we get used to working long hours, physical activity, even being on holiday. They soon become our baseline, something we possibly take for granted.