It was an exhausting, but fun experience. The first day started out alright, just a good way to start a trip like that, because it was not too exhausting and there were not too many uphill parts.
The second day was by far the hardest, but afterwards everyone was glad to finally get lunch and some rest from going uphill. It was also the coldest night. But after surviving this day, the rest was easier.
I really enjoyed the third day, with a lot of Inca ruins and even though we did not see too much because of the fog, it was extremely nice and a great walk. And Machu Picchu was the grand end to a great tour.