To the Moon demo

There exists a technology that allows doctors to weave artificial memories, such that a patient can request attempts to alter their mind, and wake up with memories of things that didn't actually happen.

However, since these new memories are permanent, the conflict between them and the existing authentic memories clash in such a way that it ceases the person's ability to properly function.

Thus, the operation is only done to people on their deathbeds, to fulfill what they wish they had done with their lives... but didn't.