Q: If I am light only, how did I come to forget it?
Nisargadatta Maharaj: You have not forgotten. It is in the picture on the screen that you forget and then remember. You never cease to be a man because you dream to be a tiger. Similarly you are pure light appearing as a picture on the screen and also becoming one with it.
[Source: I Am That]
Comments: The picture on the screen has forgotten that it actually is light. This happens due to maya. Maya is responsible for false identification & bondage.