HELP REQUIRED!!

Hi all

I am interested in knowing the origins to the phrase "What is it you're not thinking about right now?"
Is this something people are familiar with and if so do you have any sources?

Plus - can anyone tell me if this sentence is widely used (or similar) for amnesia -

"You know the feeling you get when you wake in the morning after having a dream and the more you try and think about the dream the further it goes from your mind, like a cloud bursting"

Thanks in advance!

James Brown
Professional Opportunist