Yes, you got the meaning (even if it's a quite strange one ;) ) Your translation was good, another possible way would be: and then sometimes reality punches the hope right in the face. - but yeah, you got the point! :)

die Fresse = mouth = condescendingly for the organ you use to eat ("fressen", used for animals, instead of "essen", used for humans). The English equivalent for this usage is "trap" in "shut your trap" (Halt die Fresse!) jdm in die Fresse hauen = punch s.o. in the face auf die Fresse fallen = to fall on your face You can also use linguee.de to find translations for such idioms: http://www.linguee.de/deutsch-englisch/search?source=auto&query=fresse+hauen die Realität haut der Hoffnung in die Fresse = (freely translated) Reality kicks the shit out of Hope = Hope is defeated by Reality