Special communal offerings were sacrificed every day of the seven-day holiday of Sukot. But as whereas the number of rams and lambs offered up remained constant throughout the seven days, the number of bulls decreased from 13 on the first day to seven on the seventh day. On the following day, the holiday of Shemini Atzeret, only one single bull was offered up.
וְהִקְרַבְתֶּם עֹלָה . . . פָּרִים בְּנֵי בָקָר שְׁלֹשָׁה עָשָׂר וגו': (במדבר כט:יג)
[G‑d instructed Moses to tell the Jewish people,] “You must offer up an ascent-offering [on Sukot] of 13 young bulls [on the first day] . . . ” Numbers 29:13

If we indulge the “animal” side of our personalities, always giving in to what it insists are its “needs,” it will quickly learn to assert itself and make increasing demands on us. Instead, we should accustom it to make do with the minimum, while we strive for greater and greater fulfillment in spiritual areas. On the other hand, if we try to change our animal side too abruptly, it will simply refuse to comply. We must accustom it gently and gradually, showing it step by step how spiritual fulfillment is even more satisfying than material satisfaction.

Once our material drives have been trained in this way, we can make a quantum leap and wean them entirely of their material orientation, just like the quantum leap from the last day of Sukot to Shemini Atzeret, when the number of bulls offered up drops from seven to one.1