When your conscious mind is awake its at the surface but when you start to relax the conscious mind lowers and as it lowers the subconscious mind rises up word same as a sea saw and as the conscious mind goes even further down the subconscious goes higher up but when they meet on the equal plan then you've reached the Theta State or the Lucid Dream State. At that level the mind is aware and awake but the body is asleep. Now as the conscious mind drops down further and further and the subconscious comes up then as the consciousness go's lower your awareness goes away that that's why you have on recall.