The Zohar, Chapter “Metzorah (The Leper,)” Item 10: When the time comes for the soul to part with the body, the soul does not depart the body before Divinity appears before it. Then, the soul, out of joy and fondness of Divinity, departs the body toward it. If the person is righteous, he connects with Divinity and adheres to her.
This means that when a person ascends to a higher level, the previous state fades away.
And if not, Divinity leaves him and the soul remains and walks and mourns for the separation from the body.
Allegory: When the cat does not leave the fire, sharpen the knife and the cat will follow you because it will think that you are about to cut meat. Thus, it will part with the fire. Here too, when the soul does not wish to leave the body, Divinity appears before the soul and comes out toward it and parts from the body.
In order to rise to a new level, a person must be pushed by an indirect cause. It is written, “You rise in sanctity, but never descend.” There are many ways to advance. A new state emerges only after a new, uncorrected desire is revealed. This causes the Light to disappear, as it is forced to leave the desire.
If a person has reached the state of perfection, (the state of Hafetz Hesed, where one wants nothing for his own sake), or if a person has an intention for the sake of bestowal, then how can he leave this state and start bestowing less? He must do this in order to ascend to a new level, because a person has to separate completely from the previous state. He has to be reborn in a new state from zero. How is that possible? A person isn’t able to do that on his own. For him, it means having to fall. He simply is unable to part from perfection, saying, “I give to everybody, so what else do you want from me? I cannot stop giving.”
Therefore, an additional force must intervene. For example, let’s say that a mother is having a chronic problem feeding her child. A doctor examines the child and tells her, “Your child has a stomach disorder and must not eat for two days.” The doctor must use his authority to influence her to stop giving. In the same way, there must be an additional factor that draws a person away from perfection, which is the same as death.