On my way to Shangri-La, I heard about the Tiger Leaping Gorge upper section hike while staying at a guesthouse in Lijiang. 14 miles long, undeveloped, and takes 9-10 hours, I knew I had to do it. It ended up being quite the adventure...
Altitude sickness is physical distress from difficulty adjusting to lower oxygen pressure at high altitude. I've never had altitude sickness, and never thought much of it. I will not underestimate altitude sickness again. The night I spent at the hostel in the mountains was probably one of the more difficult experiences in recent memory.
Major symptoms of altitude sickness include: headaches, fatigue, insomnia, nausea, shortness of breath, and diarrhea. Unfortunately for me, I had all the above. I was tired, but could not fall asleep. Due to a constant shortness of breath, I felt like I could not get enough oxygen. I became dehydrated, and ran out of water at around 2:00 AM. There was drinking water, and all the shops were closed. To make matters worse, I also got diarrhea, which made my dehydration worse. I wanted to hike down to lower elevation, but it was still pitch black. I went back to my room and tried to fall asleep, which was not very successful. When the it finally became bright enough outside, I packed up my stuff and hiked down the mountain. It was quite an experience.