According to Sefer Yetzira, the month of Kislev inspires a tendency toward sleep, but the Jewish people overcome this tendency, and strengthen their desire for holiness in this month. Kislev is also connected to the tribe of Benjamin.

Kislev is linked to the kidneys and to desire:

The name of the month Kislev is derived from the term kesel, and the kidneys are called kesalim, and desire comes from the kidneys. [The term for kidneys, kelayot, derives from the root kaf-lamed-heh]…meaning longing and desire.

The astrological signs of the months cause particular tendencies, but the nation’s patriarchs worked so that the Jewish people would be able to overcome these natural tendencies:

It can be explained according to the words of my honorable, holy father, our master, teacher, and rebbe [Rabbi Avraham Bornsztain, author of Avnei Nezer], that the twelve tribes correspond to the twelve months of the year. Namely, the astrological signs cause people to be naturally drawn toward the quality that the astrological sign in question dictates, and the twelve tribes acted in righteousness so that Israel could overcome the astrological sign and not be drawn after that which is prescribed by the astrological sign, for there is no astrological sign [that affects] Israel.

The natural tendency in the month of Kislev is to sleep, but the tribe of Benjamin turned this into a desire for holiness:

The opposite of the attribute of desire is [the attribute of] one who performs actions lazily, and “sloth casts a deep sleep” (Proverbs 19:15); therefore the astrological sign of the month of Kislev calls for sleep, and relates to the stomach, but Benjamin, in his saintliness, changed it into his attribute, the attribute of desire, and it is called Kislev, which is an expression of desire. (Rabbi Shmuel Bornsztain, Shem MiShmuel, Rosh Hodesh Kislev 5672)

Further reading: For more on the influence of astrological signs on the Jewish people, see A Concise Guide to the Sages, p. 423.