Yesterday I discussed the unreasonable expectation, promoted by the Na Nachs (a sub-set of Breslover Hasidim), to be happy all the time. It is remarkable that the Jewish calendar has periods of "enforced" communal sadness, while it does not have similar periods of happiness.
We are in such a period right now: known as the Three Weeks, it is the period between the 17th of Tammuz and the Ninth of Av (Tish'ah Be'av). Customs vary among communities, but the more commonly-observed minhagim include not holding weddings, not cutting one's hair, and not eating meat or drinking wine other than on Shabbat or at a se'udat mitzvah (a festive meal celebrating a berit milah / circumcision or the conclusion of learning a tractate of Talmud). Another similar period is that of sefirat ha-'omer, the period of the counting of the Omer between Pesah and Shavuot.
While most of our holidays are joyous, and we are told that in the month of Adar (leading up to Purim) our happiness increases, there are no similar periods in the Jewish calendar during which we add special behaviors that make us happy. It is indeed curious that the ancient rabbis instituted periods of sadness, but not parallel periods of happiness. Were they trying to limit our joy?
Perhaps happiness is best appreciated when the opposite is occasionally mandated.