There are two opposite ways of serving Hashem, expressed in the verse “and the angels rose (‘ratzo’) and returned (‘shov’).”
A Jew has an extra divine soul, the Neshama, which is entirely spiritual, and stems from G–d’s Essence. Even after it becomes vested in a body, it is “truly a part of G–d.” The Jew also possesses a Bestial Soul, which pursues the body’s physical needs and desires.
The Neshama naturally regards the body and the Bestial Soul as restrictive and burdensome, and longs to transcend the limitations of the physical and revert to its original state of self-nullification in unadulterated G–dliness. This yearning is called ratzo, which literally means “rising up.”
However, the Jew is not meant to sever himself altogether from the physical. Hashem sent the Neshama down into the body for a purpose: to reveal G–dliness in the body, the Bestial Soul, and the physical world, and this requires that one come into close and regular contact with the physical. In order to accomplish this, the person must disregard his ratzo desire to transcend the physical, and force himself to engage with the physical for the purpose of refining and elevating it. In so doing he implements the task of shov, which literally means “returning.” The implication is that one descends and “returns” to one’s G–d-given mission after experiencing the high of the ratzo.
Serving Hashem involves a constant, careful balance between ratzo and shov. Although they are opposite forms of divine service, they complement each other:
One who engages in shov alone and neglects the needs of his Neshama to be inspired and elevated above the physical, runs the risk that his involvement with the world will pull him down into decadence and sin. He is then not only unable to elevate the physical, but he becomes a slave to it. Ratzo enables one to function effectively in the world by elevating one above the natural desire for the physical felt by the body and the Bestial Soul.This enables the shov, which includes the involvement in the physical, to be carried out with the pure intention of fulfilling Hashem’s will, and not because one wishes to indulge the body and the Bestial Soul, or even satisfy their needs.
Conversely, one who engages in ratzo alone neglects to fulfill his purpose in the world. He deprives the world of the G–dliness that he is able to reveal within it, and, since his divine service lacks balance, he also runs the risk of falling from the peak of spirituality to indulgence in gross physical lusts that will greatly distance him from Hashem.
 Tanya beg. ch. 2.
 Ibid. ch. 37.