This article from Ars Technica covers some interesting new research on the science of memory, and why our memories deteriorate over time. It is because we push them out of the way in order to integrate new ones.
When these five findings are considered together, they provide strong support for the hypothesis that cortical pattern suppression have a role in human adaptive forgetting. This article presents convincing evidence that new memories may overwrite existing ones through adaptive forgetting, and contributes substantially to the growing literature showing that forgetting may be nearly as important as remembering in humans.
— Roheeni Saxena, Suppressing Old Memories Key to Learning New Ones
I am fascinated by this.