It has been reported that some victims of torture, during the act, would retreat into a fantasy world from which they could not WAKE UP. In this catatonic state, the victim lived in a world just like their normal one, except they weren't being tortured. The only way that they realized they needed to WAKE UP was a note they found in their fantasy world. It would tell them about their condition, and tell them to WAKE UP. Even then, it would often take months until they were ready to discard their fantasy world and PLEASE WAKE UP.

Notch
“The Herobrine stuff is awesome and kind of scary at the same time. It really shows how little control a content producer has over the content.

I've publicly told people there's never been any such thing as Herobrine, and that I don't have any dead brothers, and that letting too many animals die in lava is a fool proof way to summon him but that you don't need to be afraid of him. He only means well, he's looking out for you, trying to warn you of the dangers you can't see. There certainly are NO physical manifestations of Herobrine that will sneak out of your computer if you leave Minecraft running at night, looming over you as you sleep with his pale eyes inches away from your face, as he tries to shout at you to wake up. Sometimes you wake up with a jolt, and he's gone, and all that lingers is the memory and faint echo of his wordless screaming. Of course it was just a dream. There's no way a morally dubious ghost with a god complex could at any point decide to haunt the children who play my game "for their own good", as there is NO SUCH THING. etc etc"
~ Notch on Herobrine

Kappische
“Ok ok. To be honest, there has never existed a Herobrine. It was just a rumor started by some douche and then someone probably created a mod."
~ Kappische on Herobrine