However, it is important to know, that when a person rectifies the Nefesh and returns afterward in the next gilgul, in order to receive his Ruach (as we described), in order to rectify the Ruach, if (in this gilgul) he sins with whatever 'chet', he does not damage the Nefesh (if he was able to, then his gilgulim could continue forever). So when he receives his Ruach [his purpose would then be to rectify only the Ruach], if he damages it through a sin, it is only the Ruach that is blemished (damaged).
So he would require [as many gilgulim as is necessary] to rectify the Ruach, and in these gilgulim, his Nefesh and Ruach will enter the body together until he completes the rectification of his Ruach. Then, when he dies, he will return in a new gilgul with his Nefesh, his Ruach, and his Neshama together in one body, until he completes his Neshama. If he sins, he only damages (blemishes) his Neshama. This is how we explain the concept of Tikkun haRuach.