It is very difficult for me to eat with my mouth closed?

My mouth just isnt big enough to chew with my mouth closed. If I was to chew with my mouth closed, I would probably only get about a half inch of clearence between my upper and lower teeth. PLUS, my nose is ALWAYS congested which makes it IMPOSSIBLE to chew with your mouth closed... why do people make such a HUGE deal about people chewing with their mouth slightly open? I find it a tremendous pain to try to chew with my mouth completely closed.... makes me not even want to eat