When we are dreaming we do accept the dreams as real while we are sleeping, but when we wake up we then know it was just a dream. Still it would be easier to confuse regular dreams with past experiences or memories. When lucid you know it is a dream the whole time even when asleep and upon waking. I agree with krookedking on this one, but since it is the "norm" to have regular dreams and not lucid ones it still just blows my mind as to why one can even do it to begin with.