Just as one gathers the produce from the field and brings it into the storehouses, so too, he gathers the spiritual fruits of the mitzvot that he has fulfilled during the year, and brings them into the heavenly storehouse. Before placing produce in one’s storehouses, he must clean it of all refuse, and likewise, before bringing Torah and mitzvot into the heavenly storehouse, we have the Days of Awe, during which we cleanse ourselves of all spiritual waste.

The analogy of bringing the produce into the storehouses on Sukkot:

The festival of Sukkot is also called: “The Harvest Festival” (Exodus 34:22). It is known that all physical matters are analogous to spiritual matters. Therefore, it is evident that just as in the physical realm this is the time for gathering all the produce of the field, so too, in the spiritual realm, all Torah, mitzvot, and good deeds that a person has accumulated over the course of the year are gathered on Sukkot.

To be able to store one’s spiritual harvest, one must cleanse it:

And just as in the physical realm, we first remove any waste from the produce, and only afterward put it in the storehouse…so too in the spiritual realm, with regard to all Torah, mitzvot, and good deeds: If they contained any unworthy thoughts or any outside considerations that were not for the sake of Heaven, these are like chaff in the produce, and we do not put such mitzvot in the heavenly storehouse.

On the Days of Awe, all spiritual waste is purged:

But on Rosh HaShana and Yom Kippur: “Wholly wicked people are immediately written and sealed for death” (Rosh HaShana 16b). My holy father, our master, teacher, and rabbi [Rabbi Avraham Bornsztain of Sochatchov], of blessed memory, said that just as wholly wicked people are included in this principle, so is every aspect of every person and every mitzva. The evil part of every individual is purged and the waste from every mitzva is expelled. It is therefore obvious that after Rosh HaShana and Yom Kippur, when all Torah, mitzvot, and good deeds are cleansed of waste, it is the most auspicious time to put them in the heavenly storehouse. (Rabbi Shmuel Bornsztain, Shem MiShmuel, Sukkot 5672)