Inception

1.Dreams feel real while we're in them. It's only when we wake up that we realize something was actually strange

Well in dreams we can make impossible things come true but when we wake up its not there. We make unrealistic beliefs when we sleep and we wake up in the reality that it will never happen.

2. Dreams within dreams is too unstable

If we dream too much of something impossible then we can be very unstable since it will really be hard to accept the fact that its only a dream.