"When you die, you normally have only one simple wish - to return and tell them - "Hey, guys - it's OK! No need to feel sad! Cause you know what? It's actually OK on both sides, really." But returning is not easy - the only way would be dreams - "half-dreams" - "ghost-dreams". The problematic part is if you get stuck - you turn into a demon. Hard to say what exactly it is, but we presume it's a painful and useless existence. Better to avoid doing this,