On a deeper level, Reb Nosson explains that forgetfulness is an aspect of sleep, since it is due to our lack of awareness that we forget things. Furthermore, in Likutei Mohoran I, 19, Rebbe Nachman explains that sleep is an aspect of Klipas Noga. The sefariim hakedoshim explain that Klipas Noga is the spiritual reality that exists in between the realms of kedushah and tumah. Thus, it parallels the Tree of Knowledge of Good and Evil, since it contains both the aspects of light and darkness mixed together.
Our job in this world is to push away the negative aspects of Klipas Noga and purify (“mevarer” in Hebrew) the positive aspects and elevate them into the realm of kedushah. Thus, regarding forgetfulness and sleep, this is our avodah as well. On the one hand, we must try to remember Hashem as much as we can. Throughout the day, we should do our best to push away the desires of this world and all of our problems that make us forget about the Creator and fall asleep in avodas Hashem. On the other hand, we must also use the positive aspect of forgetfulness to break ourselves free from the past and do the mitzvah at hand with a full heart. When discouraging thoughts enter our minds, we must go into “sleep mode” and completely block them out.
