The Meaning of Yom Kippur
Yom Kippur is the day when the construction of the spiritual vessel is completed. Reality consists of Light and vessel. The Light is the Creator, or the pleasure, and the vessel is the creature, the soul, or Malchut. The Light is in complete rest and never changes. Its only purpose is to delight His creatures and bring humankind to eternal bliss.
The entire process of building the spiritual vessel, from its current, lowest state to the highest, eternal, and complete is expressed in this world in the “Ten Penitential Days” between the New Year and the Day of Atonement. During these ten days, the soul, which originally consisted of nothing but a desire to receive, gradually acquires the qualities of the Light. This occurs from the first day of Rosh Hashanah (the first day of the year) to the Day of Atonement. During this time, the soul changes in ten ways, or ten Sefirot, the foundation of the soul’s correction.
At the end of the ten days, the soul completes its correction and is ready to receive the Light. On the tenth day, the Day of Atonement, it is forbidden to display any desire to receive, emphasized by the prohibitions against eating, drinking, and the other limitations on this day of fasting. That day completes the final correction.
After the Day of Atonement preparation begins for the reception of the Light by the (by now) totally corrected soul. The reception of the Light is executed on the seven days of Sukkot by the performance of the Mitzvot of the Lulav (palm branch), the Etrog (citron), and the other Mitzvot necessary to extend the Light into the vessel.
Finally, the holiday of Simchat Torah (Rejoicing of the Torah) sums up the process, and the Light of the Creator completely fills the prepared vessel. The Torah symbolizes the Light, and the Simchah (joy) symbolizes the reception of the Light in order to bestow upon the Creator.
This correction doesn’t have to be on these precise dates; in spirituality, it can happen at any time. We only denote this process in our world on specific times of the year.