The ספר התודעה speaks about the special mission of the Jewish people over the generations. When Moshe first asked the Jewish people about their responsibility, they responded with נעשה, we will do.
The second time they were asked, they answered with נעשה ונשמע, we will do and we will hear. This latter declaration referred to the observance of the actual Mitzvot.
The first declaration of נעשה, is described as יעוד, or the special destiny of the Jewish people. Israel accepted their role of teaching the world morality. They were also told that they would be different from all of the other nations. Their special role would not be easy. It was likely to come with hatred and persecution.
We see today how needed we are in fulfilling our destiny. The world needs to learn about Hashem and the Torah. We must make Hashem King of the world. Hashem’s laws are the ones that will help make the world a better place. A system of justice that is not focused on G-d is destined to fail and be perverted. This is a very central idea of Shavuot. We affirm once again that we will live up to the challenge made to us on Mount Sinai. We must not falter in fulfilling it.