The author of the Tanya explains the “hollow of the sling” as the experience of the soul that is repeatedly confronted with its failings in the course of its lifetime in this world.
It is hurled “from one end of the universe to the other” as it is wrenched, over and over again, between its present state as a being aware of the divine truth and desiring to cleave to its source in God and the pettiness and profanity of its past actions.
In our experience, we know this as the agony of memory.
Remembering and re-experiencing past trauma is a major factor in much of our spiritual suffering.
—Rabbi Adin Steinsaltz