Our bodies naturally release chemicals after we wake up that break down the memory of your dreams.

This is why lucid dreamers keep logs next to their beds so they can write down as much as they can after waking up. 

Our bodies naturally recognize the need to separate delusion from reality as a survival mechanism. 

Sometimes people like to say things like "you can believe anything you want" "all beliefs are good" "dream away you special little dreamer, you!" But our bodies, nature, knows different.

The ability to separate delusion from reality is critical for survival. It is a big part of an organism's "fitness" in an environment. 

Basically this is broke down most simply as pattern recognition. 

Or "IQ". 

The interesting part of pattern recognition is that people will hold themselves back to preserve their fantasies ignoring patterns because they destroy an already established narrative that they have clung to.  

Cognitive dissonance.

This is self-retardation. 

Quite literally. 

Many people celebrate their refusal to recognize patterns. Proclaiming their loyalty to their fantasy as a character strength. 

This is self retardation with participation rewards (comfort).

This is all just because fantasy is fun and reality is dry, also sometimes scary too. 

You have to learn to stop depending on your feelings and to stand on principle. 

The house of cards cannot stand the storm.