Well that’s not quite so easy according to a recent study presented at the Neuroscience 2017 conference in Washington.
Roy Cox and his colleagues at the Beth Israel Deaconess Medical Centre in Boston found that the brain is pre-disposed to dwell on and strengthen negative memories while we sleep.
They tested almost 60 people by showing them both neutral and unpleasant images to different hemispheres of the brain and recording electrical activity which showed that the images had been localised in one hemisphere.
Twelve hours later they were given a memory test. Those subjects kept awake in the interim remembered roughly equal numbers of unpleasant and neutral images. Those who slept remembered more negative ones.
This suggests that “sleep selectively stabilises emotional memories” and would confirm a number of ideas about how information is “tagged” e.g. by emotions or even sounds, that make it easier to be recalled.
With people suffering PTSD or similar the trick is to find a way of reducing the emotional content. That to me is the more interesting aspect of this kind of research.