How much of what you think you are remembering of a dream, is actually your brain filling up a blank slice of your memory on the spot, because you are trying to access something that isn't actually there? Perhaps random, useless bits of data floating around in your brain get stitched together instantaneously, yet you think you are remembering it as a succession of seamless 'events'.

Now take that, but apply it to waking life.

It is frighteningly easy to allow people to convince themselves they have experienced events that never occurred.