Why is it so hard to tell that you're in a dream when you're dreaming?
Do you ever have dreams, and in those dreams, everything around you will change; the surroundings, the people you're interacting with, the time period, and hell, even the person who you are might completely change in an instant.
And yet you don't notice it at all?
You only realise once you wake up and think back on the dream. A particular one I'm thinking of is one where it started out as me staying the night at Dexter's house from Dexter's lab. Over the course of the dream, Dexter had turned into one of my friends, and we were at my house, and then 2 burglars came in, killed my friend, held me down, and started biting the tuners of my guitar.
This seemed like a pretty standard situation while I was asleep, though obviously I was scared. It's funny how I was so startled when the burglars appeared, but not when the surroundings and characters involved completely changed.
There's also the crippling sensation of having those dreams where you spend the day with a certain girl you've been wanting to be with, and you're thinking "yes, this is the kind of moment I've been waiting for, my opportunity." and then you wake up and are like "oh shit, not again", and reality bites you in the arse once more.
Dreams are weird, mang.