[Rough translation] And know, that when this Tzaddik enters into him to help him during his life in the secret of Ibur, as we described, and not in the secret of gilgul (reincarnation), he is close to the reward, and far from a 'hefsed' (loss). This is, when this person does mitzvos he shares part of his reward with the Tzaddik. This is also the secret of what is written, that "the Tzaddik shares part of his share with his friend in Gan Eden."
And understand that this is a deep secret, and we are not going into this in-depth here. However, if the person acts with evil (becomes bad), the Tzaddik does not have any punishment or loss from him, and he is not required to stay in Ibur with him [he is there only for his good, not for his bad]. On the other hand, if the person returns and undoes what he did already to rectify his soul, the Tzaddik can separate from him and go away from him.
The reason for this is, from what we explained, that the secret of ibur takes place in the life of an Adam (a person), and [the Tzaddik] is not stuck or connected with the body of the Adam like a Nefesh of the Adam would be. So when a soul enters into the body at the time it is born, it is connected to and stuck there in a complete entanglement, and it is not able to leave from there until the day he dies.
Nonetheless, the Nefesh of a Tzaddik that enters into him in the secret of an ibur, he enters at his will, and he leaves at his will. If the person remains in a state of Tzedek, the Tzaddik will always continue to dwell with him (so that he can take part in his actions), and he will stand there until the person leaves from the world, and then they will both go up together to the same [high] level [of the Tzaddik], as explained.
But if this person becomes evil in his actions, the Tzaddik will become fed up with his company, and he will leave him. This is because the Tzaddik isn't standing there in a fixed way, but rather, he is on loan, like a hospitalist staying in the owner's house until the time that he sees fit. And if he [the Tzaddik] does not find comfort there, he will go. For this reason, when some suffering happens to this person, the Tzaddik does not feel sorrow [for him] at all, and he doesn't suffer with him. Rather, he is not stuck there, but rather, he has only loaned himself to this person.