We all know how important it is to be happy, as the Torah tells us
תַּ֗חַת אֲשֶׁ֤ר לֹֽא עָבַ֨דְתָּ֙ אֶת הֹ' אֱלֹהֶ֔יךָ בְּשִׂמְחָ֖ה וּבְט֣וּב לֵבָ֑ב מֵרֹ֖ב כֹּֽל.
As you haven’t served God in happiness, with of all you have…
In other words, all of the curses and rebukes that follow are because of a lack of happiness. This is strange, because up to our parsha the Torah has not mentioned even once a mitzvah to be Happy – Not on the festivals, not after the exodus or the giving of the Torah, not even once.
In our parsha There are no less than seven mentions of a mitzvah to be happy