“The festival of Sukkot (Tabernacles) is referred to by a number of names in the Jewish sources, but no epithet seems to reflect its essence as much as that given in the prayerbook: “The time of our rejoicing.”
Such a definition, however, raises some fundamental questions:
How can a specific date in the calendar be set aside for rejoicing?
How can one obey an injunction to rejoice on a certain day, irrespective of one’s mood or condition?
The fact that this is possible is abundantly clear in the way that Simchat Torah, the final culminating day of the eight-day festival, is celebrated.
Not only do believers rejoice, but they frequently manage to draw others into their dancing and gaiety.
It is difficult to distinguish between this obligatory happiness and purely spontaneous manifestations of individual and communal joy.
The commandment to rejoice on Sukkot is in fact just one of a number of such obligations that concern one’s mood.
The Jewish calendar designates days of contemplation, of mourning, and of joy.
Though at first sight it may seem to be a paradox, it can be said that only he who has the strength to mourn on Tishah b’Av (the anniversary of the destruction of the Temple and of other disasters in Jewish history) is capable of rejoicing on Simchat Torah.
In spite of the apparent polar differences between the two activities, there is a profound bond between them, for both draw upon the same inner strength.”
–Rabbi Adin Steinsaltz
From “A Time for Joy” in The Strife of the Spirit by Rabbi Adin Steinsaltz