[Despite how casual Joshua is about all this, he's watching Hiro intensely. He really doesn't feel like getting punched by a teenager going through puberty. That slot's been taken by someone else, after all.]

The difference is that dreams exacerbate it by making you relive or rexperience whatever happened, sometimes with different scenarios. Alternate universes where you or people you know make different decisions. Even intensities vary from one night to another.