I recently received a message asking for help. After speaking with the person who sent it, I decided to share the situation anonymously, because it is a very typical one.

She said she had broken up with her ex-boyfriend many years ago, yet over the years she would still suddenly think of him at certain moments. Whenever she talked about that relationship, she could recount the scenes from their time together all the way to the breakup in great detail. Several friends around her had long served as her listeners, repeatedly hearing her version of those memories.

But not long ago, while moving and sorting through old belongings, she found the diary she had kept during that relationship. After reading it, she felt a strong disgust toward herself.

In her current memory, many things from that relationship were supposed to be proof that her boyfriend had wronged her, failed her, or owed her something. Yet in the diary, many of those same incidents looked, to her now, painfully melodramatic and unreasonable. She even felt that the person in those pages resembled the kind of woman she herself would usually criticize online.

What frightened her most was that the diary seemed to contradict almost everything she had been saying for years. She had always believed that her ex had cheated on her, betrayed her, and that she had chosen forgiveness, thereby maintaining for herself a noble and magnanimous role in the story. But in the diary she wrote at the time, she appeared to be the one pushing him to the point of suffocation. For example, if he came home five minutes late, she would lock him out.

This left her feeling close to collapse, and also ashamed. She realized that the version she had been telling her friends about her ex might have gradually become an entirely different story. And because those friends had heard her repeat it for years, she worried they might now see her as mentally unstable.

There are two common ways to talk about memory. One says that human beings fabricate their own memories. The other says that people preserve the most beautiful, purest parts of experience, and that these parts remain untouched.

I am firmly on the side of the first view: memories are altered. This does not mean the other position is simply wrong. Different studies have their own evidence and conclusions. But I believe memory can be revised because I have seen too many situations in which the earlier and later versions of the same event no longer match.

A very common example: when adult children talk to their parents about sadness or pain they experienced in childhood, the answer they often receive is, “We don’t remember that.” Even when the parents do remember, the story each side holds onto may be completely different. Whether it is the parents trying to preserve their authority and identity, or the child holding on to resentment, each person’s memory tends to contain a version they trust more—or a version that benefits them more.

Everyone remembering their own version does not mean the truth never existed. It only means people are often more willing to treat the part they believe as the truth. Memory makes this even easier.

Some time ago, I spoke with a friend about his memories. He is very sensitive about the idea of reshaping memory—turning it into a story, a novel, or any kind of processed narrative. To him, certain memories are beautiful and pure. They exist as a separate space from his present self, so he is inclined to believe they cannot be tampered with.

I like to challenge him on this, so I told him that memories are all, to some degree, products of reconstruction. We did not continue that discussion very deeply. It is the kind of topic that might make both people wake up in the middle of the night someday. Especially when a memory one person regards as precious also has another version in someone else’s mind, its purity can collapse very quickly.

Of course, if those memories are only treated as one’s own accepted truth, and one does not demand that everyone else recognize them as the “correct” version, life may be much easier.

For instance, after we fell out with an assistant, she reworked us into several different versions in her own world. If we had to explain ourselves to every person who heard those versions and correct each one, it would be exhausting and pointless. Once she had taken a position, and once that position had gained a group effect, our attempts to correct the story might only have created more trouble.

So we might as well remain the villains in her world. At least for her, that version helps rationalize many things she wants to brush past. It may also prevent her, during some late-night moment of sudden clarity, from realizing “it was my problem” and falling into severe self-attack.

Someone asked me today whether I planned to change phones this year. I truly cannot imagine a situation in which I would need to use an iPhone Duo. For the first time in all these years, I do not want to use the annual upgrade option.

A friend of mine understood his own logic more clearly: “For the sake of the annual upgrade discount, I have to find a use case for the Duo no matter what.”

That, in a way, is one of the functions of memory: it exists for a need.

This is especially true of memories that must be processed into another version. Reality is already fixed, but memory can invent feelings outside that reality, along with a version of “what I believe to be true.”

This is not necessarily a bad thing. When people remember, or when they receive an iPhone Duo they do not actually like, they still have to create a need for themselves. It is a way of adapting to the truth itself—whether they are willing to face it or not.