In a way, you could say the concept of memory rewriting is the overarching reason our memories are inaccurate. A study published in a 2014 edition of the Journal of Neuroscience, was the first to show that our brains constantly rewrite our memories to some extent, inserting useful, current information. It's a survival mechanism that ensures we're dealing with what's important today, not in the past, so that we can make good decisions. In the study, 17 men and women looked at objects with backgrounds (say, of farmland) on a computer screen. Then they had to place the object in the original location but on a new background screen. The participants always put the object in the wrong spot. Finally, they were shown the object in three locations — where it was originally, where it had been placed the second time, and a brand-new location — and asked to pick the correct spot for it. The researchers found that people always chose the second location, rather than the first [source: Paul].
"This shows their original memory of the location has changed to reflect the location they recalled on the new background screen. Their memory has updated the information by inserting the new information into the old memory," Donna Jo Bridge, the lead study author, said in a news release.
So, if you're now happily married, you may recall being intensely attracted to your spouse on that first date. But if you're pondering a divorce, you may instead remember not liking him very much. People suffering from depression or post-traumatic stress disorder sometimes aren't able to rewrite old memories with new information. Their old memories are stuck, unable to adapt to the present. They aren't able to see that things can be different, which can cause much angst [sources: Paul, Weintraub].