This is an explanation from the Rebbe in this week’s parsha in the sixth aliyah. The first possuk was, “Sh’ma Yisroel…” arguably the most important possuk in the entirety of Torah, Jews, monotheism, etc. The second possuk is, “VeOhavto es Hashem Elokecho…(And you shall love Hashem, your personal G-d).” The Rashi explains that a person who serves their teacher/master out of awe does so in a stressed out way: he’ll bring whatever his teacher/master wants and departs immediately.
The Rebbe explains further, adding that the mitzvah of loving G-d is not limited to a private emotional experience. The mitzvah of loving G-d is primarily how one actively carries out the mitzvos: that they should be done with love.