And this is the secret ("sod") (Shmuel 2 14:14) "No Nefesh will be rejected from Hashem," etc. Because all of the thoughts he might think [in fear that the Klipot might grab hold of him] are at the level of Nefesh only (which is at the world of Asiyah), and at that level, there is a fear that maybe he will be pushed away from Hashem because the Klipot are there. However, from the rectifications that he does to his Nefesh, Hashem (Elokim) will not push it away.
To recap, Hashem wouldn't raise up a person and give him another Nefesh higher than the one he originally had (at its source level). Because if he did this, the first Nefesh would need to remain below in its original place, and it would be pushed away, meaning -- it would be pushed away [from Hashem] because of the Klipot that are there. Therefore, we do not give him another Nefesh at a higher level -- only the first Nefesh itself rises higher to higher levels according to his actions, until it reaches Keter of Asiyah, and he is not given another higher Nefesh.
However, in Yetzirah and the other worlds, [where he receives] his Ruach or his Neshama, these remain below in their source level, and he receives another higher Ruach when he rectifies his actions, as we already described. And this is the secret of "Kadma Nodaat" (Rambam citation); that each Adam (person) is able to reach the level of Moshe Rabbeinu alav haShalom. If he wants to purify his actions, he is able to take a higher level Ruach, and then another higher level Ruach until he reaches the top of Yetzirah, and then he can do the same thing with a Neshama, until he reaches the top of Beriah, etc....