So in every generation, we take out some of the sparks [from the klipot], and we come into a gilgul (through reincarnation) into this world, and how we come is according to the level of our neshamot in our generation. Or, from the sparks in the head, or from the sparks of the eye, etc., we rectify these in this world. And there are those that come in a gilgul (who are reincarnated) to fix [a serious aveira] (requires further translating; I don't want to say this incorrectly). [When a gilgul or an Ibur happens, all of the 'sparks' of the Nefesh come with him into his new body, even 'sparks' [belonging to body parts] which were already rectified.
The rectified 'sparks' come into the body of the one being reincarnated along with the 'sparks' that were spoiled (through the serious sin that he did in the previous life). All of these 'sparks' come with him from the moment that he is born, and they do not separate from him at all until the day that he dies....