I was at a music concert. The speed was exhilarating as I flew for what seemed like 400m in a curving trajectory at around 60-70 kms per hour, with very clear vision. All of a sudden, I felt myself slowing and realized my brain chemical flying fuel was spent. In the end, I tried one levitation of just a few meters and couldn't even manage it - my flying fuel tank was empty. I found it interesting that whatever this brain chemical lucid-flying fuel is, it certainly seems to be in limited supply.