The Gemara (Megillah) tells us that the verse in Megillas Esther (8:16) refers to special Jewish events. “The Jews had simcha” refers to Yom Tov. “They had sasson” refers to Milah. What does this mean?
Simcha and Sasson
Simcha refers to physical pleasure whereas sasson refers to spiritual fulfillment. Thus, when one celebrates a Yom Tov meal it is mean to stimulate the pallet and bring joy and simcha to the body. The mitzva of milah brings great spiritual satisfaction to the family.
The Vilna Goan explains that simcha refers to the excitement present when one begins something new and sasson refers to the fulfillment of a great accomplishment. Milah brings great fulfillment as we train our children to dedicate themselves to the service of Hashem in the most intimate way.