This should not be translated literally. Words like attempt and effort in English are almost always followed by a phrase describing what the effort is about, or who makes it. In this case, προσπάθεια is a feel-good word, especially in combination with εθνική (i.e. everybody joining in together for some good cause). possibly moment of national importance, or time of national importance, or some such expression, would capture the patriotic spirit of the original.