Scholars are increasingly beginning to realize that memory is not perfect. It is selective and at times very creative. Hence, human memory is malleable. This means that it can certainly be influenced by internal and external factors. For instance, if there is a traumatic external act that takes place in a person's life, it can have enormous impact in a person's memory. They can fixate on it and it can haunt them. Or they can repress it and forget about it for a long time. For these reasons, it should not be surprising that these events shape a person's memory and even life.
As for internal matters, things like imagination, human desires, and passions also have a huge impact on memory. The strongest evidence for this comes from mental disease, such a schizophrenia and split personalities, but there are other minor examples, such as when a person has delusions of grandeur.