Loosing an ability

Last night I had my LD #6, and this one was very clear and stable. Only one thing surprised me: In all other 5 LD I no problem flying and so it was in the dream at first. But somehow I lost that ability the middle of the dream.
After I got lucid, I walked down a street observing the scenery and the people. After a while I decided to fly up to a roof top to watch everything from another perspective. I had no problem flying up there but once I was on top of the building I lost confidence that I could fly down again. I tried to take off and nothing happened. Because I was in a dream I decided just to jump down again. As I jumped, the building must have shrinked tremedously because it only felt like jumping off a chair. Anyway, back down on the street I tried to take off again and - nothing ! Gravity just wouldn't release me. :(
I hope I'll regain the flying skill in my next LD.

Just like you said, it seems like you simply lost confidence. Mabye try doing something to regain it; perhaps jumping off a cliff to start a flight?

Flying is weird. Sometimes it doesn't work for some reason or other. Don't worry about it. Worrying will only make it worse. It'll return and practice helps.

This happens too me so much, even when not in a lucid dream.
I display some cool power like telekinesis or flight or even duplication, but I always are unable to repeat it.
:(