The reason being is that you seem to get a different reaction when you wake up depending on the dream. Say, for example, in your dream you completely bombed a fate-deciding test in school. Then you wake up in a cold sweat and you're like " THANK GOD!!! " Of course, other dreams make you fairly depressed when you wake up. Just a few nights ago, I had an interesting dream. I can't remember a lot about it (Lots of weird stuff, I guess), but here's a part that stood out above the rest: I guess I was on my way home from school, when lo and behold, my secret crush met me by the main foyer of the school. Just seconds later, WE KISSED!! It was great!!! I asked her if this was a dream, and she said that it wasn't. Meh. Turns out a few minutes later, I'm in bed at 6:45 in the morning and instantly going from this to this . Basically my point is, well, dreams are weird.