I went on a brain injury course last year and the guy running it said your brain can only hold on to memories for 30 days, if you remember something longer ago than that, you're simply remembering remembering the event rather than the event itself, if that makes sense. He said he had recently met up with an old friend he'd not seen for 20 years and they reminisced about old times but their recollections of the same thing were completely different and contradictory.
One of my favourite examples is when City fans slate David Brightwell for his dreadful showing against Kanchelskis in the 5-0 OT derby when in actual fact he never played in that game.
Another football one is that Newcastle were cruising to the title 12 points clear in 96 when Ferguson, being the psychological genius that he is, decided to wind Keegan up, got him rattled and United came storming back to win the title. That was simply not true. Newcastle were 2nd with only a few games to go when Keegan had his rant, it played no part in them losing the title.