People have speculated that sleep is meant to organize your thoughts for years. I know when I worked in a Neuroscience lab years ago that is what many research

People have speculated that sleep is meant to organize your thoughts for years. I know when I worked in a Neuroscience lab years ago that is what many researchers thought. But to say it is to "Forget" is almost certainly an over simplification. It might be to optimize to remove the extraneous, but that is probably not all of it either. Nothing about how the brain works is simple.