Do you ever have a dream where something either really sweet or lame happens, but it's not dream-magic'y or unusual? It's something that very well could have happened in real life. It just didn't; it only happened in your dream.
Except, the brain thinks it DID happen? There's never a point where you sit up and think "I have a new memory". It's just there in your memories like it really happened, sometimes for a day or two before you realize "wait, wtf?"
That crap happens to me all the time. For atleast the last 24 hours I've been a little down because Obama didn't win reelection, for example. I'm not trying to start a whole political convo thing. I'm just saying, that junk really happened. Then it unhappened. Stop screwing with my reality, brain!
p.s. Before that, last thing it happened with was some movie I'd really been waiting to see. Woke up looking forward to seeing it all day before suddenly realizing "sonofa.... I've still got weeks to wait!"