I was with my nephew and his friends and we headed straight to top of the mountain, which is approx. 11,000 ft., to do our skiing.
By lunch time I was dead, had a headache and all I wanted to do was lay my head on the table and sleep.
I struggled thru lunch then afterwards, headed down the mountain with another guy to ski at a much lower level where I finally recovered. I had never experienced that before........
You can acclimate but it takes time. I live at 7500’ and when I go to sea level it feels like breathing oatmeal.