One experience I have which was making me crazy. When I was a teenager and spending time in our yard I saw these small light balls flying around in the evenings and at night. It happened many times. Then I asked my family to come and see because they didn't believe me when I told them. I said see for yourself. They looked around and didn't see anything. Just thought I was crazy. At last I figured out what it was. My eyes work slowly when adjusting to changes of light. When I came from inside where was a bright light to the dark backyard, where there were only yard lights around, my eyes made rapid focuses on all those lights while scanning the yard. So the small lights stuck on my eyes and it looked like lights were flying as my eyes moved rapidly around. It was fixed later on and haven't seen them anymore.