When I was in my 20s, I was a machine. Honestly, I could simply not understand why people would take time off of work. Now, some 20 years later, I get physical

When I was in my 20s, I was a machine. Honestly, I could simply not understand why people would take time off of work. Now, some 20 years later, I get physically exhausted around 6 months after the last extended vacation. Of course I don't mean to a point where I couldn't function properly any more, but I do feel way tired and low on energy. Age really makes a difference, believe me.