In the 1980s and 1990s there was a nationwide (and apparently worldwide) hysteria about satanic cults abusing children.
https://en.wikipedia.org/wiki/Satanic_ritual_abuseAs I child I regularly heard the debates on various talk shows (I watched alot of TV). What was happening was that child psychologists were effectively implanting memories into these children. I found that idea fascinating.
At some point I came up with a game that I would play on the bus ride home from school. There was an undeveloped, partially wooded lot that the bus passed by every day. People would leave things there, especially kids. But the important thing is that week-to-week and even day-to-day the lot would change. Kids might build a fort; somebody might leave or take away some trash; the neighbor might cut the grass or clear some dead wood. The game consisted of 1) noticing something that had changed and 2) inventing something that changed. The next day I would try to pick, before passing the lot, which was the real change and which was the one I invented, and then confirm as I passed.
I very quickly realized how incredibly easy it was to create false memories. Even though I was the one deliberately picking the false memories, I regularly fooled myself. In fact, I got really good at fooling myself. If you visualize an imagined scene and mentally interact with it--imagine walking through it, imagine fake relationships between elements--then for all intents & purposes your memory of it will be little different than if you had been looking at and interacting with something real. Even more scary, I learned that I could consistently misremember things; that is, for a good fake memory I'd consistently pick it day-after-day, even though each prior day I would have realized it was the fake one.
Another thing I learned with my game is that memories are largely about associations, especially plausible associations. We filter particular memories by how well they fit together and how well they comport with the larger narrative. (Which is I think why visualizations are so powerful, as they make it easy to create many elements that fit well together.) If a memory doesn't fit into other memories, like you rationally know you couldn't possibly have been somewhere on some particular day, we tend to discard it. For innocuous memories (e.g. maybe some thought of doing something at the time, but which you didn't actually perform) we filter these out almost imperceptibly. OTOH, sometimes it's difficult to rule out memories, particular innocuous ones, which is why we misremember small stuff so often.
One small thing I've avoided ever since then is looking at photographs. I've found that the mere act of looking at a photograph can almost instantly replace your own memory of an event. That doesn't mean my original memory was any more truthful. But the original is often imbued with certain emotional artifacts that, in my experience, can get washed away by the visual fidelity of a photograph.