In his first Ma'amar on Lag Ba'Omer (18th of Iyar, 5711), the Rebbe explains how the Counting of the Omer is connected to purifying and rectifying the animal soul, and that there are two elements: the rectification (Beirur)of a person's mind (Mochin) and the rectification of a person's attributes (Middot). In turn, the Rebbe explains that these two rectifications are connected to the bringing of the Omer offering and the counting itself.
The Omer offering is brought from barley (animal food), and the Talmud teaches that a baby does gain the intellectual capacity to speak until he's tasted cereal, which indicates that the Omer offering is connect to the intellect, the Mochin of the animal soul.
After the rectification of the intellect comes the rectification of the [emotional] attributes, both on a daily basis and on a weekly basis. There is a "general" rectification on the level of Makif (surrounding, not penetrating) and a "specific" one that goes into the detail of each of the seven emotional attributes and is properly internalized. The idea of the step-by-step, slow, deeper and detailed rectification is expressed in working on the subdivisions of the emotional attributes, until one's thoughts, speech, and deeds are as they should be. This is the idea of taking each day to work on a subdivision, Chesed shebeChesed, Hod shebeHod, etc.
The Rebbe also explains what certain subdivisions represent. For example Chesed shebeChesed symbolizes that out of the love one has for Hashem, he loves also what Hashem loves. When one sees someone studying Torah and fulfilling mitzvot with fear of Heaven, that inspires love for that person. Chesed shebeChesed also inspires a person to fulfill the Torah and mitzvot him/herself with great alacrity.
Gevurah shebeChesed means that love for Hashem causes a person to hate those that are against Him. Tiferet shebeChesed is related to love for the beauty and sweetness of the Torah and mitzvot. Netzach shebeChesed is the determination (out of love) to study Torah and fulfill mitzvot against any obstacles, and Hod shebeChesed is related to the idea of fighting with any outside forces that are trying to prevent him from his goal. Yesod shebeChesed is related to a deep soul connection [foundation] to Torah and mitzvot, and Malchut shebeChesed is bringing oneself [and all the above] to a state where all his thoughts, speech, and deeds are solely connected to Torah and mitzvot.
The Rebbe further explains that all the good qualities above have a negative counterpart. The subdivisions of Chesed for example, can be rooted in the love for physicality that takes him away from G-dliness. A person may, G-d forbid, take all the of the above (the love, the hate, the beauty, determination, etc.) and apply it to the physical.
The Rebbe points out that Hod is also connected to the idea of acknowledgment. Hod shebeHod, which is the Sefirah for Lag Ba'Omer, represents a level of acknowledgment that is intrinsic to this characteristic, unrelated to reason or even to the higher emotions. It is the lowest level of holiness - even if one bows during Modim (the prayer of thanks/acknowledgment) without even knowing why, there is still hope for such a person, and he/she is still connected to holiness.
The task of Rabbi Shimon Bar Yochai was to connect the highest levels of holiness to the lowest ones, and that is why his highest revelations, which he revealed on the very day of his passing, were on the day of Hod shebeHod.
[Now that Chanukah and, L'Havdil, Thanksgiving (celebrated together for the first and probably only time in history) are upon us, may we all connect to the idea of Hod, giving thanks, and renew our hope and expectation of the day when the holiness of each and every person will be revealed.
The following are the additions we make on Chanukah to the prayer of Modim mentioned above, part of the Amidah: