From Speak, Memory by Oliver Sacks
It is startling to realize that some of our most cherished memories may never have happened—or may have happened to someone else. I suspect that many of my enthusiasms and impulses, which seem entirely my own, have arisen from others’ suggestions, which have powerfully influenced me, consciously or unconsciously, and then been forgotten. Similarly, while I often give lectures on similar topics, I can never remember, for better or worse, exactly what I said on previous occasions; nor can I bear to look through my earlier notes. Losing conscious memory of what I have said before, and having no text, I discover my themes afresh each time, and they often seem to me brand-new. This type of forgetting may be necessary for a creative or healthy cryptomnesia, one that allows old thoughts to be reassembled, retranscribed, recategorized, given new and fresh implications.