The Importance of Serving G d with Joy

Because you did not serve the L-rd your G-d with joy and with gladness of heart... you will serve your enemies (Deut. 29:47)

Joy is such an important part of the Jew's service of G-d that the harsh consequence of "you will serve your enemies" does not result from a deficiency in the service, but from worshipping G-d without joy. When a Jew is happy, G-d is happy, as it were, and even the harshest decrees are annulled - analogous to an earthly king granting amnesty to his prisoners when he is in a cheerful mood.

(Chasidic teachings)

Reprinted from the Parshat Ki Savo 5762/2002 edition of L’Chaim