As mentioned in a previous post, acclimatization was a bit tougher than expected. If you should ever go to Lhasa to visit, and you travel by plane, be prepared to feel a bit sick the first days. You can take Diamox (not available in China, so also not in Lhasa) to feel better, but you have to watch out because if you have AMS (acute mountain sickness) you may not see the signs on time. In Lhasa this is normally not a problem, but higher up in the mountains this can be very serious (AMS can be fatal).
My first night was not too good with a splitting headache, and the second was even worse. I did not sleep much because of my headaches, but at least the second night it was a bit easier to breathe. Strange enough I felt quite OK during daytime. The reason is probably dehydration. You have to drink a lot more because of the high altitude, and during the daytime I keep on drinking the whole time (4 liters of water on average). But the second night before going to bed I did not drink much, I figured I drank enough already during the day. This may have been the reason, because last night I decided to drink two bottles of water during dinner, and now I felt fine. No headache at all. I still woke up a few times because I did not get any air, but then you just take a few deep breaths and you are fine again.
Today is the third full day in Lhasa, and I feel we are all used to the altitude now. This morning we rode about 10 kilometer on our bikes, and none of us was out of breath. My heartbeat was a bit higher than normal, but nothing to worry about. It seems we are ready for the trip!