Some folks, me included, like to imagine they are becoming lucid during the day. It is a good exercise( Sometimes i feel like i know in my gut that i will become lucid for having done this exercise*)

But of course one knows to be awake, not dreaming.
The fun is to challenge that certainty, and keep telling yourself that you are dreaming. And almost make yourself confused.
Just dont overdo it !

* i think it has something to do with hypnosis or trance