Likutei Moharan 135:2/ליקוטי מוהר"ן קל״ה:ב׳

12. This satisfactorily answers that which is asked in the Talmud (Sukkah 27b) concerning what Rabbi Eliezer said, “I praise those who are lazy on the festival, as in (Deuteronomy 16:14), ‘You shall rejoice on your holidays’”: But did not Rabbi Yitzchak say, “A man is obliged to visit his rabbi on the festival, as in (2 Kings 4:23), ‘Why are you going…’”? Study there well.

2For although he is one hundred parasangs away from his rabbi, and cannot come and go in one day, he is still obligated to visit his rabbi on the festival. That is, he has to discern the countenance of his rabbi on the festival—i.e., he has to honor the festival and receive the great light of yom tov, which corresponds to the countenance of his rabbi.

3For the primary holiness of the festival is contingent upon the tzaddikim, as above. And when a person welcomes the festival, he literally visits his rabbi, and as a result haughtiness is eliminated. For it is the nature of the lesser to be nullified vis-à-vis the greater.